3.7 merc 1987 water in back cylinder

[romy624]

im getting missing at idle and bogging up to about 1200 rpm then works fine replaced all electrical rebuilt carb. come to find out getting some seawater in back cylinder! wondering how this would be getting into this one cylinder????

 

[Don S]

Re: 3.7 merc 1987 water in back cylinder

Leaky exhaust riser gasket or leaky exhaust riser.
The water leaks into the exhaust manifold when the engine is not running. IF #4 cylinder has the exhaust valve open when it stops running, that is the cylinder the water goes into that leaks into the manifold.
Flush it before it rusts and get it fixed before you loose your motor.

 

[romy624]

Re: 3.7 merc 1987 water in back cylinder

hmm i put garden hose on . it dont seem to put water in there until u start it ? i can leave garden hose on when engin is off . start it takes probably 45 seconds to a minute before it starts to miss? still a riser gasket or riser u think?

 

[Bt Doctur]

Re: 3.7 merc 1987 water in back cylinder

Like Don say`s and like my response there is most likely a hole in the riser.
YOU have to remove it to check, We can`t.
Do it soon or risk losing the engine from water ingestion or a stuck valve.

 

[TilliamWe]

Re: 3.7 merc 1987 water in back cylinder

On those engines, either your exahust manifold or your riser will be aluminum. I'll bet a nickel that one of them is so corroded that it's allowing the water to leak in the exhaust chamber. And since it's at the rear of your motor, the water lays right there. And as Don points out, when the exhaust valve is open on #4 it runs in that cylinder. Common issue on many marine engines, especially that one.