Water on spark plugs.

[Reddog183]

I have a 2000 90hp Yamaha outboard. Motor ran great the last time I ran it, about two months ago. Took it down to the ramp the other day and could not get the boat off the trailer. Motor would not idle and ran like crap when throttled up. Sounded to me like carb issue. Cleaned carbs but saw no issues. Got it back together and ready to test in the yard with water hose. Motor idled great until I turned on the water. Engine died. Removed spark plugs and found that all three were wet with water.

Has anyone experienced this problem? Could it be head cover gasket or cylinder head gasket or am I looking at a much worse case?

Input much appreciated. Thanks.

[99yam40]

to get into the combustion chamber it would have to be head, head gasket, block, or exhaust plates.

Strange it is all 3 cylinders, I would look at exhaust plates to start out with. But that is just me

Or do a leak down test to see if you can tell, but kind of doubt you will be able to see

[robert graham]

Mine is a 1999 C90 and I have seen some water on the spark plugs caused by condensation, especially after sitting up for a time in higher summertime humidity...so maybe try to dry your cylinders/combustion chambers/spark plugs with air hose, ether, whatever before pulling the heads off....I believe the condensation/moisture inside the engine is the main reason for fogging the motor also....

[ausnoelm]

I don't think there would be much condensation if the motor was running, then he turned on the hose (mind you, it should never be running without the hose) the motor stopped and had water on the plugs. Did you " fiddle" with anything other than the carbs?

[TownsendsFJR1300]

Do a Leak Down test on the engine.

And if you ran that engine with NO WATER, you need to check your water pump.

It'll give you a good idea what's going on...

[zenoahphobic]

Do a Leak Down test on the engine.

And if you ran that engine with NO WATER, you need to check your water pump.

It'll give you a good idea what's going on...

Not if the water is entering thru corroded exhaust jacket as suggested earlier.f

[throrope]

When our service shop replaced our 90's water pump impeller, we also need the housing. Our tech tactfully explained how within thirty seconds the pump which rotates at engine RPM can heat beyond some absurd temperature. I always run water, but remember the one day I got distracted.

[infinityYS]

I had a situation with wet plugs, water in the cylinders. There was a hole in the exhaust plate.

[TownsendsFJR1300]

When our service shop replaced our 90's water pump impeller, we also need the housing. Our tech tactfully explained how within thirty seconds the pump which rotates at engine RPM can heat beyond some absurd temperature. I always run water, but remember the one day I got distracted.

No problem. some folks just don't know, IE;

My across / caddy corner neighbor on our canal (winter residents), would start his twin Yammies (on a 4 post lift, two levers to lower into the water) and run them dry for 2-3 minutes, OFTEN.

I couldn't take it any more watching this and hollered over to him that he was literally burning up his WP's doing that with NO water at all. Haven't seen him do this anymore. True story...