[THEFERMANATOR]

Sounds like a smeared piston. Reduced compression with a tick is a sign of a smeared pistom in the ring area. Haven't ever been in one of them old YAMAHA's, so I'm not sure if you could snake it out without splitting the case. If you could get it out without splitting it, you could do a light honing to clean the aluminum off the cylinder and replace the one piston to get it running again for awhile. On an old outboard like that I wouldn't personally sink alot of money into it since you don't know the history on it. Could be able to do just a piston for $200-300 if it isn't in that bad of condition inside. If it's all slated up from years of saltwater useage, then it can get expensive when you have to hot wrench everything apart.