Mercruiser 3.0 - Engine dies with engine cover on!

[Jdelowind]

I challenge anyone out there to solve this Mercruiser engine problem, cause it has me stumped.

The engine is a 3.0, 1985, sitting in a Sea Ray and it will run 100% perfect if the engine cover is off, or even just slid forward a few inches of where it normally sits. Weird, right? It took quite a while to figure out that the cover was somehow involved, while chasing down this problem we replaced spark plugs, cleaned flame arrestors, pulled and cleaned the fuel filters, added a new fuel filter, checked the distributor, checked the air intake for blockages, etc. The carb had been rebuilt just before I took ownership of the boat, so unless the rebuild was screwed up, there should be no problem there.

I thought it might be vapor lock causing the problem, but it occurs when the engine has just been started and is still cold. And if the engine is running great with the engine cover off, and you put the cover on, it will start sputtering and missing within a few seconds. It doesn't appear that cover is pinching a fuel line or anything like that, and there are no obvious exhaust leaks that would displace oxygen in the engine compartment

So why would an engine run awesome without the engine cover, and die within seconds of putting it on?

 

[a70eliminator]

Re: Mercruiser 3.0 - Engine dies with engine cover on!

Starving for air, that carb sucks probably about 450 cubic feet of air per minute wide open, are your intake vents clear and unrestricted? Think about your exhaust, thats how much air you need to supply to the engine for it's nothing but a big air pump sorta.

 

[CheapboatKev]

Re: Mercruiser 3.0 - Engine dies with engine cover on!

Do you have vents on your doghouse?
This can solve your problem. like JustJason said..I think your motor is suffocating

 

[JustJason]

Re: Mercruiser 3.0 - Engine dies with engine cover on!

like JustJason said..I think your motor is suffocating

Huh? when did I say that?

Take the flame arrestor off and try it real quick with the cover on.

 

[CheapboatKev]

Re: Mercruiser 3.0 - Engine dies with engine cover on!

Huh? when did I say that?

Take the flame arrestor off and try it real quick with the cover on.

starved for air...suffocating to me...didnt mean to mis quote ya

 

[JustJason]

Re: Mercruiser 3.0 - Engine dies with engine cover on!

didnt mean to mis quote ya

You didn't mis-quote me my friend.... But you may have mis-quoted
a70eliminater.

Starving for air,

That was weird... i dunno how you pulled my name out of the hat on that one. But I think you guys are one the right track with this one.

 

[CheapboatKev]

Re: Mercruiser 3.0 - Engine dies with engine cover on!

You didn't mis-quote me my friend.... But you may have mis-quoted
a70eliminater.



That was weird... i dunno how you pulled my name out of the hat on that one. But I think you guys are one the right track with this one.

Man..Sorry A70 AND JustJason..This is a perfect example of PPB...

Posting Past Bedtime!!!!

 

[CharlieB]

Re: Mercruiser 3.0 - Engine dies with engine cover on!

You said

"there are no obvious exhaust leaks"

But that is the exact symptoms of an exhaust leak, the lack of fresh air because the engine compartment is being fouled with exhaust.

Carefully check ALL exhaust gaskets, hoses, etc. Exhaust hoses age, swell and crack next to their clamps and can be very difficult to see, you may need a contortionist with a flashlight to look at some hoses, but that is exactly where you are going to find your problem.

 

[newcdnboater]

Re: Mercruiser 3.0 - Engine dies with engine cover on!

Perhaps there is a wire dangling close to where the cover mates with the housing and it is partially cut inside the insulation....cover on interrupting wire contact...cover off, wire ok. Just a thought.