Re: 75 Johnson 50 hp...no compression bottom piston.....help???
Your motor has a serious internal issue. You're going to have to take everything off if you plan on rebuilding it, so take whatever you have to take off to remove the head. Could be a broken rod, scorched piston, holed piston, broken crank, any number of things. What you've got now is junk in one piece. Start removing stuff to get the head off and go from there. If the bottom piston moves when you turn the motor over, then it might be salvageable with as little as a honing and new piston & rings, or as much as a complete overhaul. You also have to decide whether or not you want to spend the $500-$1500 to have it rebuilt - it is after all a nearly 30-year old motor. If you do most of the work yourself, you can get it down to the lower end of the scale. If you have someone else do it, it will be on the higher end, and possibly (probably) higher still.<br /><br />You can get a manual through your local West Marine, Amazon.com, here at I-boats (see bottom of page), etc. Seloc and Clymer both have positives and negatives for aftermarket manuals.<br /><br />If you get in over your head, you can part it out on eBay and use the procedes to get a newer motor. Good lower units bring a premium during the summer season as Joe Boater doesn't want to wait for Mr. Mech to rebuild that unit that was bashed on the rocks.<br />- Scott
