Backfiring Mercruiser 5.0L

homer&hob

Recruit
Joined
Nov 6, 2003
Messages
4
My 1998 Vortec motor runs perfect for 30 or 40 minutes. Then starts coughing & backfiring. Sounds like is running on 5 cylinders.
 

crazy charlie

Vice Admiral
Joined
May 22, 2003
Messages
5,604
Re: Backfiring Mercruiser 5.0L

Take off the dist cap when it does that and check for moisture.Charlie
 

johnkc

Petty Officer 1st Class
Joined
Dec 12, 2001
Messages
388
Re: Backfiring Mercruiser 5.0L

possibly the ign. sensor in the distributer.
 

denniz

Senior Chief Petty Officer
Joined
Aug 21, 2002
Messages
743
Re: Backfiring Mercruiser 5.0L

Why dont you call Scott at TIMS MARINE and get him to fix it instead of guessing?Or bring in to ftwth and Ill fix it for ya.
 

homer&hob

Recruit
Joined
Nov 6, 2003
Messages
4
Re: Backfiring Mercruiser 5.0L

scott had it for two weeks, we ran it three days and the problem returned. boat ran great for those days however.
 

denniz

Senior Chief Petty Officer
Joined
Aug 21, 2002
Messages
743
Re: Backfiring Mercruiser 5.0L

What else happens when this occurs,are you hitting waves that might jar a electrical connection ( cannon plug) loose. Are your guages dropping at all? Have you checked your water seperator for water in fuel? Could be ign sensor as previously mentioned or low voltage to it.
 

homer&hob

Recruit
Joined
Nov 6, 2003
Messages
4
Re: Backfiring Mercruiser 5.0L

I,m sorry for the lack of info. First time user.I,ve changed and checked the contents of the fuel water separator several times and find nothing abnormal. The only fluctuation in the gauge package would be the voltmeter,it seems to flicker slightly at higher RPM and more eradicly at lower RPM. One other thing, I thought it might be bad gas or water in tank and added several bottles of alcohol [approx.72oz. to 80gal.] to the fuel cell. This changed nothing. Alernater putting out approx. 15.35vdc. That's about all I can add. Thanks for any help.....H&H
 
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