Rebuilt a 72' Johnson 70hp- ran fine on hose hydrolocked on ramp

[gr82fish]

Did a complete overhaul on this 3 cyl motor with all new seals and gaskets. Flat sanded all surfaces and even used aviation sealer on all gaskets except the head gasket, installed it dry. Torqued everything to specs. It ran fine 20 min on the hose so took it to lake to try out and when I tried to start it on the trailer on the ramp it cranked over about 5 seconds and locked up. I pulled the plugs and cranked it over and water shot out at least 1 cylinder. I did have a minor water in cylinder issue before but now it is obviously much worse. What could be the problem? Thanks

 

[R.Johnson]

Re: Rebuilt a 72' Johnson 70hp- ran fine on hose hyrolocked on ramp

Re: Rebuilt a 72' Johnson 70hp- ran fine on hose hyrolocked on ramp

Sounds like you sunk that engine to deep in the water, while on the trailer. Remove the plugs, blow that water out, and get it running. To deep in the water, that engine has a tuned exhaust, it will suck in, as well as blow out.

 

[gr82fish]

Re: Rebuilt a 72' Johnson 70hp- ran fine on hose hyrolocked on ramp

Re: Rebuilt a 72' Johnson 70hp- ran fine on hose hyrolocked on ramp

Acually the motor was only in the water to just above the water intake holes and the trailer was not back far enough to back off the trailer. Any other ideas?
Thanks

 

[Chaz1]

Re: Rebuilt a 72' Johnson 70hp- ran fine on hose hydrolocked on ramp

1972 70 hp! Are you sure? Didn't think Johnson made a 70 in 1972. I have a 1972 65 hp which I believe was the motor being built for that hp range changing to a 70 hp in 1974. What is the model # on the id plate?

 

[CharlieB]

Re: Rebuilt a 72' Johnson 70hp- ran fine on hose hydrolocked on ramp

You said "used aviation sealer on all gaskets except the head gasket"
which may be the problem.

Did you assemble them wet, or wait til it almost dried?

Gasket sealers can be a good thing, but.......... they can also act as a LUBRICANT and cause a gasket to 'squeeze out' from between parts, tear and just NOT be where it is supposed to be, failing to seal.

ANY sealer should be used very sparingly and allowed to fully 'tack over' PRIOR to installation.

On the exhaust side with cooling water, leaks can and will flow into a cylinder, depending on the area of the leak and the angle of the motor at home on the hose and on the ramp, it could account for the obvious problem and not noticing it at all at home.

 

[F_R]

Re: Rebuilt a 72' Johnson 70hp- ran fine on hose hydrolocked on ramp

Are you sure you got the exhaust baffle plate flat? They are notorious for warping in that long space between bolts, by the exhaust ports. They should be replaced if warped or you will never keep water from squirting into the ports.

 

[gr82fish]

Re: Rebuilt a 72' Johnson 70hp- ran fine on hose hydrolocked on ramp

Thanks for the replies. The motor is a 70 hp, might be off a couple years. I flat sanded the plates on 1/4 inch plate glass, sure they're flat. I used sealer because I heard beforehand about leaks through exhaust area, and sparingly applied it and let it dry till tacky. Could it be a leaking head gasket? Any way to pressure check it? Thanks