78 johnson 55el binding up when crankning

[bigmike253]

Hey guys,

I just picked up a 78 johnson el55, this motor I got through my grandpa and sat unused for 10 years or so. I removed the spark plugs and shot some WD40 in there to lubricate it a bit, and spun the engine over by hand. It seems to turn freely until one point where it get very difficult to turn and then frees up again.

I removed the lower to eliminate a frozen lower unit and still acts the same. When I try to crank it over with the starter but without spark plugs it spins great. Then I replaced the lower plug and still spins great. Its when I replaced the upper plug it binds up, and stops rotating completely. I replaced the starter (because it broken when I was cleaning it up). After I replaced the starer it still binds up with both plugs in.

Any thought on what could be wrong?

[boats.net]

Usually the cylinder will get hard at the top of the compression stroke (with plugs in) because of the compression. Check all your batter connections and be sure you have a good strong battery. You should complete a compression and spark test.

[bigmike253]

Battery connections are good and shiny. If I just install top plug it still rotates to a certain point, and then stops dead. Habit hooked up to two good batteries and the starter is new.
It leads Me to think it is something mechanic in the top cyclinder. Do these engines have a pressure relief valve of any kind?

[boats.net]

No they do not. Be sure you are using the right spark plugs, check compression.

[bigmike253]

How is a compression check supposed to be performed if the engine doesn't rotate with the top plug installed?

[boats.net]

Remove the spark plugs, start with the bottom cylinder. Be sure to open the throttle all the way. If it will not turn over with compression tool hooked up then you must be having binding issues (or worst) with the #1 bearings.

[bigmike253]

I spun the engine over by hand today withno carbs And it makes a prominent hissing sound out the intake of the top cyclinder. The flywheel binds when the top cyclinder is at just about tdc, actually its 8* Before tdc and then the flywheel feels like it locks and then skips to about 1/2 after tdc when turn it by hand without plugs. Again it cranks over nicely with no plugs and doesn't make any funny noises.

[boats.net]

The problem must be internal, the only way you can find exactly what is causing is to dissassemble.