Please Help with 4.3 mercruiser dying !!

neilmw

Petty Officer 1st Class
Joined
Jul 19, 2004
Messages
245
Just been out today and was going fine for about 40 mins then noticed rpm was erratic then dropped suddenly from 3500 to 2000 then stalled, started up and found it wouldnt pick up properly, sometimes popping from the engine (carb ithink) trying to get back and the revs kept dying and stalling, then I found that if i didnt restart for a minute or two i.e leave it off it would be ok for 4-6 minutes, eventually managed to get back to the berth ok. The temparture guage was fine at around 175f, and oil pressure was good. I had a look and could see nothing untoward going on.
Now the real kick in the teeth is that I just bought the boat last week and was as certain as any one could be about an engine, even though I am not a mech I have a fairly good idea what goes on under the hood but obviously not as good an idea as I thought.....any help would be greatly appreciated. :'(
 

neilmw

Petty Officer 1st Class
Joined
Jul 19, 2004
Messages
245
Re: Please Help with 4.3 mercruiser dying !!

Cheers for that don very interesting, I did wonder if it could have been a fuel issue at first but when i found that when i left it for a couple of minutes it work fine for 4-6 minutes I wondered if it could be ign related i.e plugs or coil breaking down?
 

Don S

Honorary Moderator Emeritus
Joined
Aug 31, 2004
Messages
62,321
Re: Please Help with 4.3 mercruiser dying !!

It may very well be just a plugged up vent. An easy check to find out is to run it, when it starts slowing down, just remove the fill cap and see if it picks back up.
Or even a plugged screen on the pickup tube.
When the engine is not running whats plugging the pickup screen may fall off, and the vent may let in enough air that the fuel can get to the pump,
That is the reason for testing, so you know without taking apart and inspecting each part in the fuel system.
 

neilmw

Petty Officer 1st Class
Joined
Jul 19, 2004
Messages
245
Re: Please Help with 4.3 mercruiser dying !!

Oh I see, many thanks don, will give it a try tomorrow.
 
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