Ultimate boating sticky needed

[reelfishin]

Re: Ultimate boating sticky needed

I'm sure they're analyzing the burn, and the immediate shut down preserves the clues.

I would think that the EGT readings would do this, they are most likely preserving limited fuel or trying to calculate usage along with preserve valve train life.

 

[reelfishin]

Re: Ultimate boating sticky needed

Very interesting, I guess there are exceptions. Is this a peticular engine they have a problem with?

From what I always understood it was just a matter of the onrushing wake behind the boat forcing it's way back up through the exhaust system into the engine in the absence of exhaust pressure that would normally be there on a running engine. Leaving it run a bit isn't just to allow the motor to cool a bit before shut down it's to allow any following seas to pass or settle before the exhaust pressure ceases. I would think that the motors with the shortest exhaust travel would be most susceptible.

 

[sickwilly]

Re: Ultimate boating sticky needed

Very interesting, I guess there are exceptions. Is this a peticular engine they have a problem with?

Yeah, its just one particular engine they had a problem with (please add sarcasm!):


MCSB 97-17
Revised November 1997

Engine 'Dieseling' or 'Running-On'

MCM 4 Cylinder, V6 and V8 with Carburetors.

Under certain conditions, carbureted engines may 'run-on' when the ignition key is turned off. Normally, it will take a combination of several of the following conditions to make the engine 'run on'. These conditions include but are not limited to:
1. Type and formulation of gasoline available in the area.
2. Type of boat and its engine compartment ventilation system.
3. Outside air, inside engine compartment air and engine coolant temperatures.
4. How quickly the engine is shut off after running at cruising or higher RPMs.
5. How the boat and engine are operated.
6. Engine idle RPM set too high.
7. Wrong heat range spark plugs or spark plugs with deposits on them.
8. Deposits in combustion chamber.

Carbureted engines, unlike EFI, do not shut off the fuel supply to the engine when the ignition key is turned off. As the engine is coasting to a stop, air is still flowing through the carburetor into the manifold. This air flow can still draw fuel from the carburetor, through the intake manifold and into the combustion chamber. A hot spot in the combustion chamber will cause this fuel/air mixture to burn. The engine now 'diesels' or 'runs on' although the ignition system is not firing. EFI engines do not have this problem because the injectors do not inject fuel once the ignition key is turned off.

Suggestion to Minimize 'Run On'
Items number 1 and 2 can correct or reduce most of these 'run on' problems. Letting any engine idle a minute or two before shutting it off is desirable. This helps the engine to normalize at idle RPM before being shut down.
1. Idle engine 1 to 1-1/2 minutes before turning key off after running at cruise or higher engine RPM.
2. Be sure engine idle mixture, idle RPM and ignition timing are correct. On 4 cylinder and V6 or V8 engines with Thunderbolt IV ignition, setting idle RPM as low as possible can help stop 'run on'.
3. Try a different brand of regular fuel or try some premium fuel.
4. Increase idle mixture by 1/8 turn 'richer'.
5. Go to next colder heat range spark plugs.
6. V6 and V8 only: Install a 140o F. (60o C) thermostat.

Available Colder Spark Plugs
Original Spark Plugs in the Engine: AC-MR43T AC-MR43LTS
Colder Replacement Spark Plugs: AC-MR41T AC-None
NGK-None NGK-TR6
Champion-RV12YC OR Champion-RV91MC Champion-RS9YC

 

[QC]

Re: Ultimate boating sticky needed

Oh, go ahead, post the relevant and proper information. Jeeeeeez loooueeeeeze, anybody could do that . . .

 

[a70eliminator]

Re: Ultimate boating sticky needed

Yea thats funny ha ha, That service BULL itin sure covers it all.
any one of these conditions
any two of these conditions
or all these conditions together
or just plain being an idiot (the way boat is operated)
Sounds like a cover our butt kind of addemdum.

And you say you haven't fixed yours yet?

I have owned over 20 different carbureted V8 engines over the years and it's funny never once had one with that problem unless it was my mistake while setting a distributor or tuning a carb.