1975 Johnson 25hp, Water in Cylinders

[Brandon.S]

Hello everyone!

I'm currently fixing up a 1975 25 hp Johnson. I have a fairly large amount of water getting into both cylinders. I also have an even 120 psi of compression in both cylinders, so I'd be inclined to think the head gasket is ok.

Before I tear this thing down, or go and buy a whole gasket set, what gaskets could be blown that would let water in the cylinders?

Best,
Brandon

 

[RCO]

The exhaust cover gasket can let water into the cylinders also . Of course water in the fuel tank will find its way there too...

 

[Brandon.S]

I'll have to look there first. I suspect it's definitely a gasket leak. With the lower unit off and plugs out I can put the garden hose to the water tube (with very low pressure of course) and watch the cylinders fill with water.

 

[F_R]

That is a super major leak. Should be no doubt when you find it. Pull the head first, and if that isn't it pull the exhaust covers. If that isn't either, then you have some serious searching to do.

 

[racerone]

Time to pull the motor apart for inspection.----Water inside the motor is a NO,NO---Was the motor in the normal running position when you put the hose to the water tube ?

 

[Brandon.S]

Correct, the motor was in the normal vertical position for that test.

 

[racerone]

Looked at the lower crankshaft seal ?

 

[Chance1989]

No, is there an easy way to determine if that's bad? I purchased the entire oem power head gasket kit

 

[54bobby]

is it now, or has it ever been a salt water engine? salt water can corrode the inner aluminum, exhaust cover plate and you could replace gaskets all day long and would still have intrusion.

 

[Chance1989]

It has been in salt water, however, I had that plate off while replacing the gaskets no more then 3 hours ago. It seemed have very little to no corrosion. There was a small rust stain but I highly doubt there where any through holes and was able to scorch bright it out with a fine pad. When I had originally taken off the exhaust cover, their was a fair bit of milky oil. I thought I had the problem solved but didn't seem to go away. What are the odds of it burning residual for the 10 plus minutes of running... I'm thinking rather slim

 

[54bobby]

you said you had the plate off, you do know there is 2 cover plates and 2 gaskets correct? 1 is pancaked on top of the other. it's the inner one that corrodes through.

 

[Chance1989]

Yes, I replaced both gaskets. Is there potential for water to enter around the reeds?

 

[Crosbyman]

if compression is ok that compressed area is limited to the combustion zone ABOVE & Between the cyl. faces and the cyl head.

seeing that you have no "compressed air loss" by your readings water should be entering below the rings via the intakes ports or exhaust ports.

with both cyl ...getting water and the intake fuel channels being 2 separate zones fed fuel from the carb & the reeds I would concentrate my research on the exhaust cavity which is common to both cyl. exhaust ports.

if water is coming in from both intakes ports I would say ...major internal leak….. so start with the easy stuff

Possibly a pin hole in the exhaust plate allowing water to be spayed on the exhaust ports openings . .

Me.. I would dry up the exhaust plate area then without the engine running push water up the water tube for a few minutes then open up the exhaust cover to see if water made it past the plate gasket to the exhaust cavity next to the exhaust ports

 

[Chance1989]

Thanks for the reply!. Okay, I will try that when I get out of work. Also, Someone else had mentioned lower crank seal... could this be the culprit by any chance?