4.3L Mercurser Diesels Backfires on shutdown

[GAV10]

Just bought a used 19 ft Stingray with a 4.3L V-6 Mercruser, 97 hours on it. The engine runs very well except it diesels and backfires for 10 to 20 seconds after shut down. This is a carb. model, not EFI. Any suggestions on what would cause this.<br /><br />My first post.<br /><br />Thanks...<br /><br />Mark

 

[Bear]

Re: 4.3L Mercurser Diesels Backfires on shutdown

First post? <br />Try here:<br /> http://www.iboats.com/cgi-bin/ubb/ultimatebb.cgi?ubb=forum&f=24&submit=Go <br /><br />Good luck!<br />

 

[dmorley]

Re: 4.3L Mercurser Diesels Backfires on shutdown

I've got the exact same problem. At first my spark arrestor was pretty plugged up and the problem when away after I cleaned it. Problem came back a few days later and a boat mechanic, who was too booked to work on it, told me I would need an entire carborator rebuild. Unless somebody indicates otherwise that is what I'll have done.

 

[akita]

Re: 4.3L Mercurser Diesels Backfires on shutdown

COULD BE CARB IF IT IS LEAKING SOME GAS INTO THE INTAKE. BUT IF IT ISNT THE IDLE MAY BE SET TO HIGH. BOTH OF THESE WILL CAUSE THIS.

 

[roscoe]

Re: 4.3L Mercurser Diesels Backfires on shutdown

A lean running engine will do this. Carb adjustment or cleaning may fix.

 

[moderator1]

Re: 4.3L Mercurser Diesels Backfires on shutdown

Moving to I/O questions.

 

[jee70611]

Re: 4.3L Mercurser Diesels Backfires on shutdown

Check to see if the motor is timed right. It could be off just enough to cause your problem, but not so far off to cause you to notice it that much. Also, check your plugs for excessive carbon build up. Some carbon may be getting hot enough to create a "hot spot" that will continue to ignite the air/fuel mixture after the ignition is shut off. Try decarbing it. I can't think of the name of the stuff you use off the top of my head, but I'm sure someone hear knows(Seafoam? ). At least for the time being though, try letting it idle for a minute or two then put it in gear(at idle speed of course) right before you shut it off. Don't let that keep you from getting the problem fixed though. Good Luck ! <br /><br />James

 

[akriverrat]

Re: 4.3L Mercurser Diesels Backfires on shutdown

http://www.marinemechanic.com/site/page154.html

 

[Northern Eclipse]

Re: 4.3L Mercurser Diesels Backfires on shutdown

Gav10 what grade fuel are you using sometimes using too high of too low a grade (octane rating) can cause pinging/knocking or diesling