Old 7.5 hp merc, money pit or salvageable

[dynamic]

I picked up a 1971 merc 75 outboard this winter. It turned over in the guys garage, but I did not do a compression check when I bought it ($200). When I got it out on the lake I found it could be started, barely, and reved up, again barely. Today I finally hooked up a compression tester and found the top cylinder to be at 90psi, the bottom one is at 70psi. Both holes have spark. I bought this with the idea that it could be a trolling motor to push my old 70's fiberglass boat slowly around the lake .

I don't really think I want to spend a fortune fixing such an old motor up but I think the carb needs rebuilt to get it idling/running. I know the compression is poor but I don't want to pull it apart and overhaul the engine. My question for you is if you think it will run for awhile if I only rebuild the carbs, or should I just get rid of it and not poor money into a dying cause?

 

[tashasdaddy]

Re: Old 7.5 hp merc, money pit or salvageable

in a barrel, (big garbage can works, keep hose running so the can stay full) do a decarb, it cleans the crud out of the engine, and has been known to free up rings, and bring up compression. it will smoke like it's going to blow up. you can use regular seafoam, in a spray bottle instead of Deep Creep. who knows how long it will run, it may out last you and me. clean throughly & rebuild the carbs, and do this.
http://forums.iboats.com/bbBoard.cgi?a=viewthread;fid=36;gtid=1035563

 

[ddennis]

Re: Old 7.5 hp merc, money pit or salvageable

TashasDaddy is right! Decarb..I didnt believe in it till I did it on my 15hp Johnson...brought the compression up really well..motor runs better than it ever did!

 

[cguettler]

Re: Old 7.5 hp merc, money pit or salvageable

I have a similar motor that was rebuilt when I bought it. It ran like a top. However, in the next couple of years things started to fall apart. It seems like everytime I get it up and running something happens shortly after. Some of the things I could repair others had to go to the shop. At this point in time I would have been better off buying a new motor. There is nothing worse than getting to the water only to break down on the water or not to be able to get your motor running once you get to the water. I hope you have better luck than I have. I am about to run it back to the shop today.