84' Johnson 25HP lost power and died

[JJGulley]

We have a 1984 Johnson J25RCRD, Engine has always ran without any issues. suddenly lost power and then died recently. We have checked everything we could, clean bright blue spark, cleaned and drained fuel, fuel pump working, cleaned the carb. and fuel lines, nothing found faulty but for a slight amount of water found in the fuel can. . Engine just didn't feel right when pulling to start it. I Ran a compression test on each of the two cylinders. Both read the same, only about 45psi. I know the compression should be up near 90 to 100 psi. what would cause both cylinders to read the same with the low compression, possibly a bad valve plate? or a crack in the block? Looking bfor a few pointers on where to dig into with this. Any help would be appreciated.

 

[racerone]

There are no valves that have anything to do with compression on that motor.-------Pull the cylinder head off as you may have a bad head gasket.-----You have checked / replaced the water pump impeller recently I hope.-----And you are mixing gas and oil at 50:1 ratio ?

 

[JJGulley]

have not pulled the head yet, water pump impeller is fairly new and was exhausting water normally, Fuel as always 50:1 with Premium, no ethanol

 

[oldboat1]

But you said there was a "small amount" of water in the fuel can. Was that corrected? Talk about that some more.

The intake is down at the bottom of the tank, where any water would be located.

 

[JJGulley]

Yes that was corrected, fuel lines purged and cleaned. no detectable water present, carb. pulled, no water was present in the bowl, hooked the engine up to an alternate fuel tank to attempt re-starts. engine turns freely with no binding or noise present. I'm hoping for a blown head gasket as you mentioned.

 

[Bttb]

Blown head gasket small amounts or water in cyl at idle will cause to kill

 

[tomhath]

Head gasket is inexpensive and very easy to replace. Find a piece of plate glass or something else that's known to be flat so you can smooth the head out before putting it back on. Also get a torque wrench that measures inch-pounds and follow the tightening pattern.

 

[JJGulley]

Turns out it was a blown head gasket between the cylinders

 

[Bullie]

Very clean in there. Must have had a little water like you said.