No load WOT test/block heater suggestions

[John Dickson]

I have DD 671 TIs. The cover sticker says max rpm 2500 NL. I need a description of how to perform the no load test, what the test reveals, what to look for and potential adjustments to make as a result of the test. Can anyone tell me what the max rpm under load I should expect . Perhaps there is already a thread on this subject. Excellent forum!

Second, I would like to install block heaters. I am looking for recommendations on manufacturers of block heaters or perhaps pad heaters.

Thanks for all the excellent information and comments. You all keep me off the streets and out of the bars!

 

[Boss Lady]

Welcome to the forum!

 

[Passages]

Are you sure you have that right? I have 6-71TI's and my sticker says 2500 loaded, 2650 no load. The No load test is quite simple to perform, out of gear and engine warm, push the throttles to wide open. Record the readings off the tack or better yet, use a phototach. This will tell you whether engines are capable of running to spec.

Then take the boat out. Open the throttles all the way and record the max rpm. It's important that you at least hit nameplate RPM under load. If you exceed it by 50-100 it's even better. If you can't, your engine needs a tune up or your prop needs some pitch removed.

WRT block heaters, Wolverine adhesive heater pads get high reviews. 500 watts/engine should do it.

 

[REBrueckner]

BEFORE performing RPM tests, with engines OFF, have someone else advance throttle speed (Morse) control to maximum speed, watch the fuel control lever advance at the engine....then use your finger at the engine to manually advance the fuel control lever further...if there is more movement, throttle cables/controls need adjustment. Disconnect the cable if necessary to check the fuel control lever.
Cable fastening may be loose, or throttle control component loose..I have found both over the years...

 

[SKYCHENEY]

Go to www.wolverineheater.com for the pad heaters. Also, if you search here you should be able to find the post by Karl (Genesis) of how to hook them up with theromostats for automatic operation.

 

[Trojan]

Mine also say the same thing as Passages. You hit the nail on the head Passage. Well if you are not a diesel mechanic and it sounds maybe not like it. You can do the test, but if its bad. Get a diesel mechanic to do a complete tune-up while you watch. If YOU do it wrong and have a runaway. Good by motors. Maybe even the boat. There is nothing much worse than a hand-grenaded motor.

BILL

 

[rmaher]

I have the Covington marinized 6-71ti and the valve cover label says "Max RPM NL 02500." If memory serves, the loaded WOT is 2300.

Back to this gentleman's original question (or perhaps a tangent thereof), does reaching these targets evidence a good base motor? Would you need a compression check if these numbers are obtained or would your time/money be better spent looking for other issues?

 

[Genesis]

If the NL speed is 2500, then max loaded is going to be 200 off that typically, or 2300.

Reaching NL speed just means the governor is set correctly. Reaching max WOT doesn't mean the engine is otherwise ok.

However, if you run my "30 second compression test" (search here for it in the FAQs) and ALSO reach WOT+50 with a full load in the boat, compression is PROBABLY ok.

On a 6-71 (inline) I'd pull the airbox covers and look, since its EASY to do. Its much, much harder on the V engines due to the manifolds being in the way. There its a far tougher call how involved you get verifying things if you're reasonably sure the compression is ok.

 

[gyee]

Go to www.wolverineheater.com for the pad heaters. Also, if you search here you should be able to find the post by Karl (Genesis) of how to hook them up with theromostats for automatic operation.

How would you remove the Wolverine pad if you had to replace it?

 

[SKYCHENEY]

I think you could scrape it off if you had to. I would start with a sharp wood chisel and try to work around the edges until it came loose. It would not be easy with limited room to work, but I think it could be done without too much trouble.

 

[Nick]

Welcome aboard!!


I have the 671TIs and the nameplate is the same as Passages and Trojan 2650 NL, 2500 load.

I have the "Kim Start" block heaters in cooling system near the fuel pump. The heater coils are inserted in the football shaped fitting in the block near the fuel pump. The heaters are immersion type heating elements with electric thermostats. I think the heaters are 500 or 75 watt each. The thermostats are installed in the cooling system manifold. I installed the thermostats 3 years no problems with either the heating elements or the switches. The block heaters are plugged into a 110v outlet in the bilge and keep the engines at about 120F. I leave the heaters on all season at the dock, early spring through late November. Nice quick starts little smoke, dry engines.

 

[John Dickson]

Thanks for all the replies enginemeisters! This site is addictive, no doubt. I double checked my engines on the WOT rating. The blue OEM DD stickers say 2500 NL WOT, HOWEVER the covers have larger stickers stating 2500 wot load and 2650 WOT noload - must have been added by Johnson Towers as part of the marinization? I presume the JT conversion adds the extra 150 rpms? So is there a consensus on block heaters? Blanket or immersion?? I am in Detroit - cold springs and falls definitely. (Very cold today - 20'). My DDs are in heated storage this winter. Thanks again for all the help.

 

[SKYCHENEY]

Well, you can't beat the price of the pad heaters.

 

[Genesis]

Pads are great BUT make sure they are solidly attached AND on a flat (no imprint, etc) surface! They WILL burn up if not.

6-71s typically have a usable "football" port into which one can put immersion heaters. If you use them, either use a thermostat or use 220V heaters but wire them for 110V (this results in far less wattage, and then they can be left on safely)

6V92s and some 8Vs have that port consumed for the exhaust manifold cooling - if so your only rational choice is the pad heater option. That's what I did - one 250W one on the side of the oil pan, and another on the oil cooler housing.