Hey everyone I'd like to start out by introducing myself my name is ray and I am new to this site and to boating as well. I just bought my first boat it is a 15.5 ft venture pacer II bass boat. when I bought the boat he gave me two mercury 850's with it he had no info on them other than the one on the boat will not run because when he bought the boat he tried to run it dry for a few minutes to make sure it ran and the belt broke when he tried to remove the pulley he gummed up the pulley by using a huge gear puller. Let me just say I don't know a whole lot about boat motors by I am mechanically inclined enough to fix these with some guidance. The motor on the boat now is a 1973 mercury 850 and the spare is a 1974 mercury 850. My real question here is are the parts off of these motors compatible and if I should work to buil one good motor out of two of them or should I see if I can just get the spare one running. He told me he's never tried so I'm sure their is a reason why. But with no info on these motors ie. last time ran or anything I'm not sure if their is anything I should check before trying to just run them. I apologize for making this so I was just hoping to cover everything.