Block Heaters

[eze2bme]

I have a 1979 43DC and have just installed block heaters on my J&T 6-71N's (Wolverine 750 watt heat "pads" that attach to the bottom of the oil pans). I have also installed a remote sensor thermostat that will cut off the heaters when the engine compartment reaches a pre-set temperature. My question is: at what temperature should the heaters cut off? I'm leaning towards 75 degrees mainly because the heat from the engine room will rise into the rest of the boat. Any thoughts? The manufacturer of the block heaters said that they must be cut off once the engines are running to prevent burning up the heaters. Thanks.

[Traveler 45C]

I’m thinking 70F is the magic number.

Can you provide details on your install and where you obtained your parts?

Thanks,

Greg

[Boater261]

Is there any risk that these heating pads can cause a fire? What if oil drips onto them? Do you need a thermostat cut off? Are oil heaters better that heaters installed in the the water jacket in the block?

[Bob Bradley]

Well, this post finally got me off my duff to look at heaters. I did a quick search and found www.padheaters.com, which explained installation basics. Basics seem like pretty much all you need. Then I looked at www.wolverineheater.com/products.shtml, (http://www.wolverineheater.com/products.shtml,) where I found sizing and prices. Looks like the model 40 - 500 watt will do nicely for my 6v92's.

I phoned them, and learned that all I need to do is clean the bottom of the oil pan with Brake Kleen spray, and peel and stick the heater. They assured me that the adhesive will NOT let the heater drop off. The unit measures 5" x 7". Here's some specs on how effectively they work: www.padheaters.com/test_40.html (http://www.padheaters.com/test_40.html)

Price is not an issue: $69.95 each on the Wolverine site. I ordered 2.

The fellow on the phone didn't like thermostatically controlled units. Recommended just leaving them plugged in when it's cold.
Bob

[Dick]

I only have mine set at 55 degrees. Even with canvas snapped over the air intake and exhaust ports, I figure most of the heat goes out through the ports rather than finding its way into the rest of the boat. I wouldn't bother with 70 or 75 degrees unless you can really stop the cold air from entering the engine room. Only then might it make sense.

Dick

[Genesis]

I would PREFER immersion heaters (safer in terms of potential risk if the heater was to detach), but that's not possible with most of the 6V92s, as the only port available (the square port on the side of the block) is consumed for one of the exhaust manifold cooling connections, and Kim Hotstart (who makes the only port-based heater for that engine) does not make a replacement panel with a pipe connection integrated to the heater (they DO for some other Detroit applications!)

As such, the Wolverines are probably the best option for many of us Detroit owners....

[surfdancer45]

Be prepared for a stiff elec bill if you run 500-770 heaters at full wattage. Tony Athens (boatdiesel.com) recommended hooking the heaters up to a 110 receptacle that is wired in series which cuts the watts in half. I did that and my engines stay nice and warm, in a really cold spell I just switch over to the other side of the duplex for full wattage. Bob

[Boater261]

Genesis - I have 6-71s and am told that you can get an immersion heater (Kim Hotstart or J.Jeb) that fits into the block right behind the oil cooler (supposedly there's a cover there that you simply remove and bolt the heater right in). Then all you have to do is plug the heater into the 110 service. I'm told you can also buy an additional control package to provide for constant temperature and auto shut off. Seems too simple but if it is that simple I like it better than the sticky pads on the bottom of the pan as with the Wolverines. I would greatly appreciate any light you can shed on this.

[Geoff58]

Ive been following this thread with great interest. I investigated oil/block heaters and (through Sierra Detroit Diesel) found, what I feel is a much better alternative.
Instead of just heating the oil/pan and having 'some' radiant heat warm the block, I purchased thermostatically controlled, fresh water heating/circulating pumps (110v).
Think about it. These pumps push hot water throughout the block, keeping the entire block warm, not just the oil. Any smoke traces at start (outside temps in the 40s) were completely gone.
Easy to install, bulkhead mount, 110v,2 hoses, two bypass shutoff valves. Took about 1.5hrs each.
After having had "oil" heaters, Id never go back.
BTW, thank you all for a great forum. Ive learned more here in the past year than bringing our '78 58yf from FLA to Ca this year or in my 30 years of boating!

[Genesis]

What did you pay for the forced-circulation heaters and is there an online place I can look for information on them?

I have concerns about these, just as I do with thermal siphon tank heaters. The primary ones are mounting considerations and plumbing related - you have to run quite a bit of hose around for these, and that adds significantly to the risk of cooling system failures. You also need flow control to avoid bypassing the engine during normal operation - this would require (at minimum) a check valve and "reverse" flow from the heater, so that the check valve would close when the engine is started. Finally, you need an interlock so that you can't crank up with the heater enabled (or vice-versa, an automatic shutdown of the heater if you attempt it) otherwise with the check valve you'll have stagnant coolant in the heater which will likely lead to an overheat and burn-out of the unit.

I really would have preferred to install the Kim Hotstart units in my 6V92s, but there is no way to accomplish it. The "alternate location" is not available on my engines (a 3/4" pipe plug in the oil cooler housing), and the primary, as I noted, is taken up by the exhaust manifold cooling connection.

I've looked for a solid thermostatically-controlled solution to this since I bought my boat 4 years ago, and have yet to find it for my configuration. I want something that maintains coolant temperature in the 110-120F range, cycling the heater on and off as necessary to do that, yet not creating "hot spots" (as a thermal siphon unit would.) So far the closest I've come is the Wolverine pan heaters......

[newinlet]

I have J&T 671-N's , I bought Block heater elements directly from Johnson & Towers. Just remove a block off plate just below the fuel cooler.(real easy) I hard wired the heaters to my electrical panel. It heats the fresh water side of the cooling system. In my opinion it does an great job. I live in Mass. no trouble in 2 Yrs. !!

[jlr]

Here is the setup on my 56 MY with 892's and using Kimhotstart block heaters.I bought some thermostats (adjustable) used I guess primarily for greenhouses and then wired them into a three way switch for each block heater with a red led panel for each. So, I can switch them into heat mode, or off mode or thermostat mode, all from my pilothouse. The red LED lights when they are in heat mode or when the thermostat kicks them on. Also, in each engine room, I have a digital thermometer that permits me to fine tune when they come on. I can have them come on when the engine room temps drop below , let's say, 70 degrees in the summer, and know that my diesels are warm as toast whenever I want to start them . In the winter, even though I will have winterized the engines, I can have them kick on when the engine rooms drop below 30 degrees--just to be safe. A real neat setup. Best of all, I can see the LED when lit from my CCTV system on the boat when I dial in from the computer in my office--that way I know whether they have kicked on or not.

[eze2bme]

There have been many replies to this topic, but here’s what I did. I called Tony at Seaboard Marine (800-200-2628) and purchased two 500 watt (not 750 – my error) Wolverine block heater pads for the mains and one 125 watt heater pad for the genny (about $200 total as I recall). As Bob indicated in his reply all you do is clean the paint and any oil off of the bottom on the oil pans and follow the instructions. I used a mirror, paint scraper and cordless Dremel to get the paint off and then cleaned with Green Magic and acetone. The install on the mains took about an hour each.

I installed two 110 volt outlets wired to a spare circuit breaker. From Grainger I purchased a Johnson Controls remote sensor thermostat (4E047 @ $48 – temp range from -30 to 100 degrees) which I’ve set at 70 degrees (this is what is known as a cooling thermostat as it cuts OFF at a preset temp). From Radio Shack I purchased a red indicator light which I installed into the circuit also so that I could tell when the heaters were “ON”. I realize that I could just turn the heaters ON before I needed them but the thermostat seemed an easier solution and since each 6-71 weighs around 3000 pounds I can’t imagine how long it would take to heat up that much iron! Additionally, since I use my boat year round and often “at the last minute” I wanted the engines warm and ready. Also I wanted to use the radiant heat from the engines to help keep my boat warm. Tony indicated that I could just leave the heaters ON all the time and cut them OFF after starting the engines but for my use I wasn’t comfortable leaving the heaters ON all the time. (Tony said that leaving the heaters ON all the time would get the 6-71’s to about 100 degrees if the ambient outside temps weren’t too cold.) I have a remote sensing thermometer in the engine room which keeps me informed to the heat levels.

I realize that running the heaters (1150 watts total for all three) may use up some electricity but I see it as a trade off since I’d have heat on anyway. To help prevent heat loss through the fresh air intake grilles I have made up insulated inserts that are “plugged” into the air grilles from dockside … just unsnap and remove and I‘m ready to go. (My fresh air intake grilles are the long slots rather than the “fish gill” style.)

Hope that this helps … and hope that all have a great holiday boating season!

[Captcoop]

I am in Virginia and I used Hotstart 500W heaters in my 6V92 engines. I also purchased the thermostat that is optional with the heater. It screws in at the thermostat housing and has different setting options. I used a 100/110 temp range and never ran any other heat on the boat during the winter months. I ran the heaters year round and the power bill was high in the winter but worth the peace of mind. I purchased the heaters from Covington Detroit Diesel. Good Luck

[wshelton]

There was alot of info about these heates last year at this time. Here is a ten minute fix I used that has worked great. I have 671s and bought the 500 watt Wolverine oil pan heaters. Instead of attaching the pads to my oil pans--(a lot of work), I attached them to the front of the heat exchangers and wired direct to an extra 120 volt breaker on the panel. These keep the engines warm via the water systems and made the difference in cold start ups. I do not run the engines with the heaters on and l have left them on while away without much difference in electric bill---I'm running heat year around if needed and never winterize due to pleasent climate here so I am accustomed to a bill of some sort.

[Genesis]

I'm surprised that worked well (attaching the heaters to the side of the H/E tanks)

Since heat rises, I'd think that would stratify the coolant (since you're heating the very top of the system) and wouldn't produce much heat in the engine itself.

How warm/hot did the engine blocks get?

That's a really cool implementation if it can be made to work due to the ease of installation!

[eze2bme]

Tony's telephone number is: 800-200-2628 ....

[jim rosenthal]

..here's another plus to pan heaters...I usually end up winterizing my engines after the boat is hauled, like this year. I also change the oil, and because of peculiarities of 3116s I am limited to CAT SAEO 30wt. Which I didn't have on hand because I was thinking about other stuff....anyway the pan heaters will make it a lot easier to pump out the old oil when I do the oil change. I suppose the Reverso pump would pull it out when cold- or maybe it wouldn't, and just give up.
I used the 250watt heaters which I wired to a duplex outlet in the engine room on a separate breaker on the Hatteras electrical panel. I shut them off before starting the engines. They have stayed on fine, and the engines start instantly and don't smoke. Mine are actually on the sides of the pans as there is very little clearance between the bottom of the pan and the bilge. But they work great, didn't cost much, and have given no trouble so far.

[edgewalker]

I have a pair of 671tibs in my 1996 39 express and in the fall of 2002 went down to beaufort N.C. to fish for bluefins.By december it was so cold it really took alot to crank over the engines.So since I was docked at jarrett bay ,and they were doing some custum work anyway,I had the detroit guys at the jarrett bay yard install block heaters.The cost for having the job done there was more then reasonable and it was the best thing I ever could do for those engines.I had AC outlets installed right above each motor and when the boats not running I leave them on all the time.That winter the engines would almost always kick over on the second try and in the summer they start up immediately with no smoke.They also cut down on the humidity in the engine room,which is extremely helpful on cutting down on the rust factor.I would suggest to anyone with 671s or any detroit engine that your being foolish by not having them especially if you keep your boat anywhere cold.

[boater260]

Edgewalker - what is the type and name of the block heaters you had installed?

[edgewalker]

I have to check let you know thursday

[Roger]

Kris- can you send me details on the block heater instalation on the engines, i would like to do this now also, can you e-mail photo of the installation on the block so I can see which access plate it goes into.
e-mail rwlehm@aol.com or call me you have the #. Do you have part numbers etc. and do you have a separate thermostat in the water manifold to contro the temp. and how are they wired. thanks Roger

[Genesis]

Note that the Model 40s do not work well on these engines unless you can drop the pan.

Unfortunately there are raised logos and part numbers all over the bottom of the pans. The sides are not big enough to mount the heater pad, and my attempt at going on the bottom ended with one unit destroyed due to overheating (improper contact due to the stamped raised areas)

If you could drop the pan you could fix this, unfortunately, that's unreasonable fro most of us.

I am trying to get a 250W unit which I think will fit on the SIDE of the pan, or on the oil cooler housing. Either should work out, and in cool but not stupid-cold areas, the 250W units should be enough.

I'll soon know.

[Walter Pereira]

Karl..

I went to the Wolverine site and was just getting ready to place an order for the 500 W size for my 6V92's. Good thing I read your last post. I live in Jersey and we do get some cold winter nites at times, but I do the regular winterizing routine. I just thought it would be a good idea to add these heaters in order to prevent dampness etc. and as Jim mentioned, it may help in oil changes.

Do you think all 6/92's have the same problems with raised letters etc? I think I will wait to order mine until I hear from you or if anyone else has done it. Another thing comes to mind however, what about 2 units of 250 W on each engine, one on each side of the pan... Let me have your thoughts.

Thanks... Walt

[Genesis]

That's an option. Its more expensive, but allows you to power up only one or both.

I was pretty pissed off. I thought I had good adhesion, but of course the best you can do with the engines mounted and pans mounted is to use a mirror and feel.

Looked good right up until I turned it on. Oops. :D

When I pulled the blown one it was obvious what had happened. When the instructions say there must not be ANY protrusions, they mean it. The numbers were burned into the underside of the pad where it smoked.

That was the only shot available that I had on my oil pans in terms of placement - all the rest of the possibilities were MORE obstructed in terms of projections and such than where I put them.

What might also work well is one 250 on the side of the oil pan (inboard) and a second on the oil cooler housing. That would warm both coolant and oil. The coolant being warm will keep the block nice and toasty, while the oil being warm has its own obvious advantages. The only downside is that one of them will not be visible (the oil cooler on the outboard side of the starboard engine on 6V92s) which is kind of a bummer; I like the idea of these things being where I can SEE them.

[Bob Bradley]

Well, my timing isn't quite as good as Walter's. At the same time Karl was posting last evening, I was installing the 2 Wolverine 500watt pads on the underside of my 6v92's. They stuck OK, and didn't appear to have any gaps underneath, but did smoke quite a bit when I ran them. I had cleaned the bottom of the pans with BrakeKleen, and oil absorb pads, and scraped what paint I could feel, then applied the pads.

I didn't leave them on overnight when I left, as they were obviously QUITE HOT, and I was nervous about adhesion quality. Of course I had read the installation instructions on their website, and discussed the installation with their technician when I called to order them, so I didn't bother reading the paper that came with them (directions are for wimps), and neither their site nor their technician mentioned any concern over protrusions.

I'll give them a good test for a couple hours on Saturday when I can watch them for a couple hours.

Karl, did yours burn out because of gaps between them and the pan around the bumps?
Bob

[Genesis]

... the one I tested was WAY too hot, was smoking like an SOB, and was bubbling around the area where the lettering was - and was also obviously disbonding.

I shut it off; I had an inspection mirror checking it out, and there was no way I was about to find out how bad it was going to get. It was only in the area right where the raised numbers were - the rest was running ok.

The pad might still be alive, but the adhesive is a "one shot" and I wasn't about to have a fire down in the engine room.

Now I need to get a 250 and see if I can get that to work...

[Bob Bradley]

That's pretty much what I experienced, however and unfortunately, I installed both before plugging in either. At first I thought it might just be burning paint or residue that I missed on the underside of the pan. After a few minutes, I was actually beginning to worry about the fumes I was breathing, and shut both down and ventilated the cabin.

It ticks me off that the "technician" at Wolverine didn't bother to mention that these things would spontaneously combust under these conditions. I guess I'll be scraping them off this weekend, and mailing them back to Wolverine.

[Genesis]

There can be NOTHING that causes any area of any size that has no heat transfer. If you do have that, they burn up.

I've got a 250W coming and once I figure out where they need to go, I'll put something up here.

[Genesis]

Right on the side of the oil pan, below the dipstick boss, horizontally.

This is on a 6V92TA.

It gets the oil and bottom of the engine nice and toasty within an hour or so of being turned on. Be aware that the surface temperature of these units when operating (according to my IR thermometer) is roughly 300F! Don't stick your hand on it!

VERY easy to install there.

It will ALSO fit on the side of the oil cooler, between the two hold-down bolts.

I am going to try out the one on the side of the oil pan, and if that's not enough heat, will add a second one on the side of the oil cooler - that way I'll get both oil AND coolant preheat.

If you're in a real cold area, two 250W units should provide the same performance as one 500W, and you won't get a "smoke test" this way since you can get to them easily and there is sufficient flat, cleanable space (without raised part numbers!) to mount them. In a "kinda cool" area a single 250W may be enough.

I'm going to rig permanent wiring for them including a thermostat in the E/R (will energize the heaters with engine room temp under 70F) and also a relay that will drop them off when the engines are running (rigged off the Hobbs switch) That should make the system completely automated. I also intend to put a 120V pilot light on the outlet so that you can tell at a glance if the heaters are operating or not, and verify that the light goes OUT when you start up AM.

[Traveler 45C]

Sounds like a good set up. It’s on my list on things to do. Would you post the particulars of your permanent set up when you get it done?

Greg

[Bob Bradley]

How far north are you located? My intention is to help out starting the engines during the Oct - Nov timeframe in CT, where I can expect temps to drop into the 30's at night. Water temp here is still probably around 45 -50. How much difference in starting have you noticed with the 250 watt units? Right now, I seem to have to crank and stop about 3 times before she fires up. I smoke like mad for about 20 - 30 seconds, and she cleans right up.

[Genesis]

.... I'm in the Florida Panhandle.

We get winter temperatures down to 20F or so overnight, with daytime highs in the 40s on those days.

I don't know how they will perform as a "single" in cold weather yet - we haven't had real cold weather. Ask me in another month.

You can always double them up - there's room for two, one on each side of the oil pan, or you could do what I intend to do if the first one is not enough - put one on the oil pan, as I have, and the second on the oil cooler. The latter will be at the "low point" of the cooling system, which will warm the coolant and create a convective flow in the cooling system - warming the top of the block as well.

The "recommendation" for this size engine is one 500W unit. However, as I noted in my previous post here, that unit won't fit without covering part numbers and such and that causes them to burn up when powered - so that's no good.

Frankly, I suspect that heating the oil on one hand the coolant on the other is likely the ideal situation. The 250W heater had the oil in the "nice and hot" range within an hour - within a few more hours I suspect the engine would be quite warm as well. A quick start test produced absolutely zero start-up smoke - of course it wasn't cold today, but I usually get a small puff of white - today, I got nothing.

I'll know more next week as we're expecting to get some cooler weather and I'll have both engines powered up overnight, then will start up first thing in the morning when its still nice and cool out. We'll see what kind of difference it makes and whether I need to get the second set of units.

[Walter Pereira]

Karl, My order is on the way for the 250 w units. I will put them in on the sides of the oil pans as you did. Since fire is a very real concern, do you know of any way we can rig them to turn off if they drop off into the bilge? Anyone have ideas..

P.S. At one time I lived in Bay Point in Panama City Beach and we did get some pretty cool winter nights, but nothing like we have in New Jersey. With that in mind I may opt to install a second unit on each engine. Thanks for all of your great tips Walt

[Genesis]

... and if they do, I suspect they will burn out before they can start a fire. At least I sure as hell hope they do!

The adhesive is pretty tenacious stuff - its identified on the backing paper as the 3M "VHB" adhesive that is used to attach things like "keelguard" strips. Its widely considered as radically permanent if applied to a clean, dry surface.

Tony over at Seaboard Marine in California has put a LOT of these on boats and from what he has told me he has never had one disbond. Let's hope he's right :D

[34Hatt]

What do you think if they are on the bottom of the pan which I can get to and is smooth. And in the Summer you are not using them on a long trip and come back and there is some oil on the pan due to a small front main drip. Is it going to smoke out the bilge??????
Thanks Dan

[Genesis]

.... then put them on the bottom of the pan.

The surface temp was clocked with my IR thermometer right in the 300F area. That's not hot enough to smoke oil.

[jim rosenthal]

I've had these on my Caterpillars for a year or so, they are routinely on for days at a time, I have had zero problems with them. The engines start instantly (not that I had a problem before but they don't smoke at all on startup and settle into a smooth idle immediately. And they have stuck on great. I used enamel reducer or something like that to clean the pans before I stuck them on. I have the 250w units. I am going to put one on the genset as well if I can find enough room for it.

[Jaxfishgyd]

Well after reading all the emails, I ordered two 250 watt blockheaters for my 43' Hatteras's 6-71N's.
Cranked up the motors Sunday after a slight cold spell and if there were any flying insects in Jacksonville before I did, they are now dead from the smoke.....

[boater260]

Just had two Kim Hotstart TPS small tank heaters (1,800 watts) installed on 6-71s in a 39C. Thermostat range 80 on to 100 off. Thermostat is built in but they offer an adjustable thermostat. Started right up with little smoke (touch wood but my engines don't smoke much anyway). Heaters were installed by Johnson & Tower. They ran a new water line across the front of each engine. They did a nice job. Simple installation if you know what you're doing. I wired two 20 amp circuit breakers in the engine room. Didn't have any more room in the breaker panel in the salon. I figure I'll be down in the engine room checking fluids each time before I start the engines so that I can simply shut the heaters off while I'm down there.

Roger - I couldn't use the direct immersion heaters that fit into the football shaped plate on the block. The ones manufactured by Kim Hotstart had an outlet for the hose that runs to turbo but it was only about 3/4" and my water hoses to the turbo are 1 1/4" or larger.

[Genesis]

Went over and did a cold start this AM; we had temperatures down to 40ish overnight.

The heaters had been on for a day or so.

Both engines lit off on the first starting attempt. There was a small bit of sputtering and some smoke, but it wasn't bad at all.

Normally, in these temperatures, I'd do at least one "pre-heat" cycle with the stop button pushed. That was not necessary today.

The improvement is considerable; I suspect a second 250W unit on the oil cooler housing would improve things even more. I am considering buying a the second unit, but will wait until we get colder overnight temps to make my decision.

You can't argue with the light power consumption of the 250W units.....

[Genesis]

OK, as promised, here's what I wired up.

I took power for the system from a 120V line that was in the engine room aft and is connected to a duplex outlet for utility use. First, I changed that outlet to a GFCI, since the original was just a regular outlet and the breaker not on the GFI pair for house loads.

Second, I made up two relay boxes. Those are Carallon 1-gang plastic boxes with two inlets (top and bottom.) The relays I used are 30A, rated for HVAC service, sealed Potter and Brumfield number T92S11D22-12s, available from Digikey. They have .250 quick-connect terminals and can be bolted to the side of the Carallon box with a pair of 8-32 screws and nuts - allowing clear access to the terminals. The boxes get blank covers with a label on them "ENGINE BLOCK HEATER RELAY 120V" and are mounted aft above the generator (a convenient place near the power source.)

I then ran the 120V to the power relay for each engine, and from the output of the power relay (N/O side) to a 2 gang box at the front of each engine. In the 2-gang box is a standard duplex outlet and a switch/pilot light combination. This allows you to manually turn OFF the heaters, and also to see that they are powered on. The cover is an "in use" rated clear cover box, allowing you to see the switch and pilot light while the Wolverines are plugged in, yet providing splash protection while in use.

Ok, now how to control this monstrosity.

We're going to use 12V to control it, since that's what we happen to have handy on the engine. I replaced the Hobbs switches on the secondary fuel cannister with a dual-pole unit - you now have SPDT, instead of SPST. Common is wired to 12V hot coming to the switch; N/O is wired to the Hobbs meter, as it was.

The N/C contact is wired (using a single red wire) to a cheap, $10 MECHANICAL thermostat which I mounted to the front bulkhead directly in front of the engine, near the bottom. This provides for thermostatic control - when the engine room is at or over a given temperature, there is no point in using preheat. The thermostat allows us to choose - and they're only $10 or so - its worth it for the additional energy savings over time. The output of the thermostat goes to the 12V coil terminal on the relay (another single red wire), with the other side of the coil of the relay being run back to bus negative in the power panel (black wire.) Label everything.

So what we end up with is this:

1. Thermostatic control on the engine room temperature. I set the engine room thermostats at 75F. Below that, the preheaters are on.

2. The preheaters turn off automatically if I forget to and crank the engines, as the hobbs switch will change over to run the hobbs meter. Also, if 12V power is lost for some reason (e.g. you turn off the main disconnect to that engine to do maintenance) the preheaters are also cut off, since the power to the relay coil is disengaged.

3. The entire system is GFI protected by the outlet changeover.

4. There is a manual disable switch next to the preheater outlet, and a pilot light denoting that the system is energized. Of course you can also unplug the cords, but there is no need with this system - just shut it off.

The ultimate capacity is that of the breaker; the circuit I'm on is a 20A, so I could conceiveably run 1000W per engine. All the other components are rated WAY above the feed (I used 14ga triplex wire for the 120V side, whcih is good to 20A anyway), so they're not the limiting factor.

In reality two 250W heaters (one on the pan, one on the oil cooler) per engine will be well within limits, and leave you 10A of power on that circuit for "utility" purposes while they are in use.

You're protected against forgetting to turn them off before cranking up, the system is fairly "fail safe" in that power is required to hold on the relay to energize the heaters (its not a "close to disable" system, so a wiring fault leads to the heaters being OFF) and the entire 120V side is GFI protected.

Also, the 12V wiring that hits the relay comes into the other side of the box where the 120V is, so there's a decent amount of isolation between those - important for obvious safety reasons. DO NOT leave the wires long - you don't want a loose wire in the junction box ending up on the other side! (either 120V or 12V)

The reason for TWO of everything is that I wanted to have independant shutdowns for each engine - its not possible to easily do that otherwise. While I could "cascade" the relays and feed everything in series, there's no real reason to do so, because if you can only bring one engine up for some reason you might want the other's preheat to still be operational.

You could also feed this system off separate breakers for each engine, and thus provide for much higher wattage if you wanted to.

Sensing the engine room temperature seems to be FAR better than just the engine temp. If the ER is warm, then there is no need for preheat. If its not, then there probably is - the engine won't be warm if the ER is not!

More info on request if anyone wants it....

[Traveler 45C]

Genesis,

Thank you so much! Right on time. Excellent set up.

Some questions:
Did you get the relays on line?
Where did you get the switch/pilot light combination?
Did you get the new Hobbs switch from Saunders?
Where did you get the mech. T-stats?

Greg

[Bob Bradley]

You have WAY too much time on your hands.
Bob

[jim rosenthal]

..don't listen to Bob. He's just jealous. Bet he'll ask you for the wiring diagram...:lol

[Bob Bradley]

and Mind reader.


Please, Karl?!?!?!?!?

[Genesis]

Relays are available from www.digikey.com - I gave 'ya the part number. Punch that into their search and you should find them - they're approximately $10 each. I picked on these relays specifically because they're sealed - thus, no explosion risk - even though I have a diesel boat.

The Hobbs switches came from Napa. They have 'em available. Hold onto your socks when you ask for the price - Hobbs has some wild hair ideas about what their switches are worth (they wanted over $40 EACH for them! Aeieeeee!) There may be other makers of these - any pressure range will do, really (I used the 4psi switch intended for an oil pressure warning light) - the trick is finding one that's SPDT rather than SPST, because you need both normally open (for your hobbs meter) and Normally closed (for the preheater relay) contacts.

Switch/pilot light combinations are available at Home Depot and Lowes. Standard 120V stuff. So are the Carallon Marine-UL rated boxes. Be aware that those switches, however, are NOT sealed - so using them in a gasoline vessel's bilge may be unwise. If my boat was gas I might still do it but NOT throw those switches without making damn sure there are no fumes first. The pilot lights are neon lamps so there's no risk there in terms of ignition.

Mech T-stats came from Lowes. They were cheap. They may not work out in the long term due to vibration (there's a standard bimetallic strip in there with a reed relay actuated by a magnet), but if they fail they're simple to replace with something better and were only $10 - so I figure oh what the heck. Its not like I have an "investment" in them. They are also sealed, being a reed relay - again, no sparks. I didn't want a mercury-switch T-stat, because those will get beaten to hell in a boat with all the banging around - that glass vial is pretty heavy on the end of the strip.

What do you need for a wiring diagram beyond what's described above? I'll try if I know what you're after....

[Bob Bradley]

Actually, I had a pretty good idea of what you had put together. The main motive for my post was simple, gratuituous, b@ll bustin. :evil

Being of fairly simple mind, I suspect I will take the low ground on this installation, and run a heavy duty extension cord to the aft, port duplex outlet that services my ice maker, couple that with an inline thermostat, and simply plug the dang things in.
Bob

[Jaxfishgyd]

I installed my two 250w block heaters this morning. Took all of 25 mins for the two of them.

I did cheat and put them on the side of the oil pans as on my 43' Hatteras we do NOT have a lot of room.

Do not have them wired permanently but as the forecast is for a low of 28 on Wens. will see how they crank up after I get home from work.

[Genesis]

... will be my first "real" test.

My system has been on "automatic" now for about two weeks.

Tonight we have a hard freeze expected. Tomorrow morning I am going to go do my weekly "crank up and warm up" routine - we'll see what kind of difference the singles make.

I'll either be happy or on the phone to Tony for the ones to stick on the oil cooler housings..... Will post here.

[Traveler 45C]

Genesis,

What about the genny? Is it getting enough warmth from the Mains?

Greg

[Genesis]

The genny has always started immediately, even in very cold weather. Its a Yanmar engine - guess that says something, eh?

The test this morning was quite interesting. Both engines fired off on the first try, albiet with a roughly 6-7 second cranking interval. There was some smoke, but not much, and it cleared within a few seconds.

Overnight OATs were right around 30F. It was in the 40s when I got there to do the test.

While the second 250W pad would certainly help more, the single pad seems to do the essential parts of the job. There's no way that I would have seen this kind of cold-start performance absent the heaters - no chance at all.

I think I'm going to go ahead and get the second pad, but for those who just don't want to spend the money, the single definitely does quite a bit all on its own.

[Traveler 45C]

What were your engine temps when you got there this morn’?

[Genesis]

The thermometers on the automatic controls for the heaters were showing in the low 50s. That would be air temperature in the engine room at the forward bulkhead. I have no idea if they're accurate at that temperature, but subjectively, it felt about right.

Of course the heaters were on all night - they are set to energize the heaters at anything under 75F or so ambient. Also, the floor is up right now - which means that the heaters were also heating the entire salon! With the floor down I expect the ER would have been quite a bit warmer.

The interesting thing about the pad heaters is that most of the heat is going where it can do some good - into the engine.

50F engine room temperatures would normally lead to a couple of cycles of cranking with the STOP buttons pushed before you'd get a good start. To get clean starts on the FIRST crank, with no "roll with the stop pushed" cycles, was pretty surprising.

[Traveler 45C]

Hmmm…

It would be interesting to know what your actuall engine temps were.

250W or 500W, I’m trying to decide. The 250W’s would fit nicely on the sides of the pans, real easy to install. I have room on the bottom of the pans for the 500W’s, just harder to clean up for install. I’m getting the same weather that you get.

Why are you gonna’ add the second heater?

What is exactly is your Warm-up routine?

Greg

[Jaxfishgyd]

I started my motors this evening (Detroit 6-71N) after I got home from work. Our high today was only 51 with lows overnight of 41.
(I put the heaters on yesterday afternoon and they have been on since)
Both fired up in less than 2 seconds. When I started them up 2 weeks ago, in temps much higher than this it took 15-20 secs total time each.
Looks like a "well spent" $128 !!!

[Genesis]

If you put them on the bottom of the pan, you must make ABSOLUTELY CERTAIN that the surface is completely FLAT and CLEAN. Ditto for the side of the pan, of course, but its a hell of a lot easier to make sure you have it right on the side of the pan. You can also secure the cord to the dipstick tube boss, which means that if the pad DOES detach you've got a shot at it dangling and burning out rather than landing on the fiberglass pan underneath and perhaps causing real trouble.

I burned up a 500W by attempting to put it over a stamped part number - I didn't think it was that big of a deal. I was wrong. The instructions told me so too, but I'm a guy and we regularly ignore instructions, right? :lol Result: SMOKE!

Anyway, the 250s make a HUGE difference. The only reason to put the second set of 250s on is to get even more warmth. I'm not sure its worth it, to be honest, but I may do it simply to warm the coolant as well as the oil.

The thing is, its a tough call because putting the second units on will double the energy use, unless the thermostats cycle them.

Subjectively the bottom of the block near the oil pan interface felt like it was in the upper 90s to perhaps 100F. The pan itself is quite warm, as is the oil; I have measured (with an IR thermometer) oil temps in the 140-150F range back when it was a bit warmer outside.

The issue of course is the INTERNAL temperature of the engine, which is impossible to measure. The top of the motor felt cool to cold, but that doesn't matter - what does you can't get to.

They're not "hot", but they're definitely WELL above ambient, and the difference in starting behavior is huge.

[montauk1989]

I've been involved with many diesel fired emergency generator installations. All of the engines had coolant heaters, indoors and outside. Depending on the installation, oil and battery heaters may also be used. Coolant heaters heat the engine more evenly than pan or oil heaters. Most of the engines on boats are basically the same engine as the smaller diesel generators made by cummins, detroit and cat. I'm wondering why you can't simply use a coolant or "jacket" heater. Even the 3.0 liter diesel in my car has a 400watt coolant heater. After a few hours even my valve cover is warm. It's not just the oil that needs to be warm, you want all of the internal components to be warm to avoid wear on startup.

One more item to consider with oil heaters. If the oil gets hot enough, impurities will evaporate from the oil and condense on cold engine parts causing internal corrosion. Many airplanes have oil heaters but now many owners are finding out the hard way that leaving oil heaters on is not a good idea unless you're going to fly for at least a half an hour to warm up the entire engine and allow the impurities to be blown out. Frequent oil changes also help. I wonder if the same wouldn't apply to your installation. Unlike the emergency generators, there's an awful lot of cold metal in your engine when your pan heater is on. Emergency generators are evenly warmed. Some are almost too hot too touch. They need to be because they have to start and take load in 10 seconds. No time for glow plugs. Do the engine manufacturers have any information or recommendations?

Dave

[Genesis]

.... coolant heaters on the 6V92s in marine service are basically impossible.

Why?

Because the ONLY place Detroit left for it is consumed by the exhaust manifold water tap. So you're screwed.

External 'tank' heaters are GROSSLY inferior to in-block designs for a whole host of reasons, not the least of which is that you need a circulating pump model to get decent efficiency, they're more complex (must have check valves in them to prevent reverse flow when running - and sucking cooling system efficiency), and you've now got two more long hoses running around which can fail and screw you at any time.

A second 250W pad on the oil cooler housing will heat the lowest point of the water jacket. Convection will warm the rest of the engine, since you'll get a decent flow that way.

Keeping the oil warm is a big deal; a LOT of damage is caused by cold oil, as it condenses moisture out of the air.

Oil DIPSTICK heaters are problematic as they heat the oil locally and that causes flash-off of volatiles and any contaminents. This sort of heater is a completely different thing, and I would not expect it to have the same issues. The oil temperature is only in the mid 100s after being on all night - measured with an IR thermometer aimed at the stick slathered with it after being withdrawn. It simply doesn't get that hot - just warm.

I've done standby generator installations and work before, and they're a completely different beast. Those engines are expected to start and come up "online" immediately with zero warning. A boat is not like that.

In the ideal world you'd have a pre-luber too, but I don't. Could I? Probably. But I don't.....

[Traveler 45C]

Genesis,

Do you have the Napa Part# for the Hobbs switch?

[eze2bme]

I'm in Columbia, SC on a fresh water lake and have a 1979 43DCMY ... yesterday I went to the boat ... the night temp had been 26 degrees and it was 35 when I got to the boat. Using my infrared heat gun the temp on the oil pan was 107 and the injector cover was 96 on one 671N and 106 and 94 respectively on the other. I have one 500 watt heater on the bottom of each oil pan.

By the way ... the temp in the ER was 68.

[breakaway]

any thoughts on the Kats 300 watt magnetic heaters that go on the pan

[Genesis]

... probably have it on the boat (still have the box, I think) but not offhand, no.

Any Napa store should be able to look it up though - its in their book.

[Traveler 45C]

I put the 500’s on my 8-71’s. Today’s temp was 38F when I got to the boat (over night temps were in the 20’s). Both engine blocks were at 78F and the oil pan temps was over 130F. The engine room was 65F. The engines fired immediately. What a difference temperature makes.

[Genesis]

I put a 250 on the oil pan and another one on the oil cooler housing.

The difference is amazing. The thermostat housings are WARM now, even when the boat is too damn cold, and light-off is instantaneous - with no smoke.

[Traveler 45C]

I took IR measurements at various points all over the engine. I measured between 70-78F on the blower, T-stat housing, manifolds, and valve covers, etc. Even the filters were warm. That’s surface temp. It must be warmer internally.

Thanks for your help on this.