Earlier this year I got my hands on a 1959 10hp Johnson Seahorse QD-20. It had a couple of random problems like a busted thermostat, bad water pump and I had to reset the magneto points. Before doing all this, I ran a compression test and both cylinders were at roughly 80-85 PSI (I'm not sure if this is good compression or not). This is the first old engine I've had the opportunity to pull apart and try to troubleshoot, so, I got curious about the condition of the pistons and I took the cylinder head off. The pistons appeared to be in decent condition, so I put the cylinder head back on without replacing any gaskets even though the old gasket looked kind of banged up. Finally I got the motor in the water and put it on my 12' aluminum Starcraft, however at full throttle the motor seemed like it was running at barely half speed (only a little faster than trolling speed). Could there be a leak in compression somewhere? Or perhaps full throttle with only 80-85 psi in the cylinders isn't what I quite expected. I'm going to run another compression test to see if it's still at 80-85 psi. I just started getting into fixing up smaller outboards and I was super excited to get out on the water with this motor. I guess I was just a bit disappointed with its speed. Either way it still runs and gets me where I want to go, so it's not a huge deal. Any thoughts would be really helpful, thanks!
