I have an old 1961 Mercury 700 FGS (6 cyl.) that I have been working on. I got the boat/motor from Dad, and when I started messing with it I did a compression test. I couldn't test the top and bottom cylinders since the adapter i have is too long (I could take the top cowl off to test the top cylinder but haven't). Cylinders 2-5 all read pretty low compression (~60 psi), but they are all even. The motor runs, although the idle is pretty rough at ~800 rpm. I was thinking about using Seafoam to decarb the motor. I found a post about decarbing the motor that I was going to follow: 16oz. Seafoam to 3 gals fuel/oil mix, run for 15 mins, then let it sit for 15 mins, repeat. I'm not sure how much it will help, but I'm not sure how much it would hurt either.
If anyone has any other advice or tips, I'd appreciate it.
If anyone has any other advice or tips, I'd appreciate it.