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, 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

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......