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About that 57 7.5. I had to fix the leaky shift handle so I pulled the lower unit. The exhaust to motor gasket was really rough. And the spring, o ring, and washer that sits on top of the drive shaft had not been installed correctly. Everything was black and gooey. When I got the lower end out I decided to do the water pump gaskets and seals as well as the prop shaft seal. In the process I discovered that the shock absorber was broken. Not sure if it was broken or if I broke it somehow as I had to tap the prop back on. Anyway with all that done and fixed I tackled the possible problem with the leaf plate check valves. Couldn’t help but bugger up the gaskets. They were sealed on with some kind of adhesive.
On the back side of the leaf plate are the check valves. All around them was black crude but the valves themselves looked wet and OK. Is there some way to recondition these? Somebody on the UCC site said he had never seen these things fail. Not sure where to get the gaskets yet. I ordered a pair for a 74 Johnson 6 hp a while back. Hard to find and expensive.
I’ve got plenty of intake gaskets for these engine, glad to send you the two different gaskets needed. Yeah, there should be no sealer on those gaskets, they go on dry, or perhaps coat them with a little marine grease to help them seal and stay “supple”. Perhaps some of this goop got caught in a leaf valve, or perhaps those two black pressure valves. I’m confused when you said that pressure valves are on the “back side of the plate”… The leaf valves are on the back side, the pressure valves are on the front side, perhaps just terminology confusion.
PS: 1974 6hp intake gaskets are totally different than the gaskets for your 7.5hp