hi, i am trying to start a project on a 1972 6hp Johnson seahorse outboard 2 cyl.looks good in and out. the only problem i can see is that motor will not run, was storage for a long time and i think is lock/stuck.opened the back plate where the spark plug go,look abit ugly like dark rust dirt,Is there a way I can try to unlock the motor. I sprayed W40 and waiting couple day before trying to move, if this fail is there another way I can bring this motor to life? maybe new piston?thanks
Let it soak in Sea Foam, or engine cleaner from the dealer for several hours or overnight. You pulled the head off? There'll be crud in the water jacket, but if there's rust in the cylinders then likely a complete teardown is in the making for further inspection. I assume you tried to pull the rope on it and got nothing. WD40 won't do a whole lot for you at the moment. It's okay but not really the right stuff for the job.
It is probable that the rings are lightly rusted to the cylinders. You need to free them as Mikeyzx2 has indicated.Buy a new head gasket ($10.+/-) and take the cylinder head off so that you can see the pistons. Lay the motor down with pistons up and pour the seafoam, mystery oil, or whatever, so that it can reach the rings. After a couple of days you can lightly tap the pistons in rotation around the edges with a wooden dowel and mallet. It is not likely that a rebuild would be economically justified.
It depends on why the inside of the motor is rusty. If it is just from humidity getting into the cylinder it may be possible to break it loose with oil. If the rust was due to the motor being submerged the damage could be so bad the motor would require a complete (expensive ) rebuild. Even if the rusting is only in the cylinder the piston(s) may have to come out. If rust locks the piston rings in their grooves the motor will not develope enough cylinder pressure to run.
i did took a look real good this time and is no so much as rust,but is more a type of black gum is that what you call crud?.do not look like the motor was sumerge,look like was not use for a long timeand maybe was store in a no so good place,took me some w40 and time to have the speed control moving,i did not removed the head off..i did remove the back plate where the spark plug hole are,i can see the 2 piston from there,is that a good place to pour seaform?,or still need to remove head off? thanks guys you are big help
Take the motor apart. Any torquing you do to the flywheel or hitting of the pistons can bend the rods. Those 6s have aluminum rods that are easily deformed if you really horse on them. Take the motor down to the crankshaft, press the pistons out with an arbor, clean it up, replace what needs replacing and reassemble it if it's worthwhile. Rusty bores should be dressed with a hone. Stuck rings need to be either cleaned up or replaced. Good chance there is rust on the needle bearings inside,too. Do it once, do it right....- Scott