Try to get both running before considering a teardown/rebuild. After running and warming up once, you may be surprised how much higher the compression is. Fogging oil does not create much of a seal on the rings on a motor that hasn’t been run for a long time. Be sure to use a compression gauge with a check-valve at the motor end of the hose. It will read lower if the valve is only at the gauge end due to the volume of the hose. If one or both start and run good, forget compression and enjoy it. I’ve seen too many people rebuild outboard motors that don’t need it due to initial compression numbers. If one or both need rebuilding, and you find parts (they are out there), you can easily spend more than the motor will ever be worth, so it may be better to buy a motor that can be demonstrated running good; unless cost is not an object and you really enjoy the rebuilding part of the hobby for fun. When you ran compression test, was the choke open and the throttle cracked open a bit? You measured compression by pulling the rope. Did you disconnect the linkage to the compression relief valves first? If not your readings will be low. You may find a significant compression increase using the electric starter. Using electric start, you also don’t have to disconnect the compression relief valves to check compression, as they only are linked to the recoil starter. You can crank it by using jumper cables – get a good connection to the starter first and then connect the cables to the battery to crank, as it’s hard to connect to the starter when the motor starts moving on its shock mounts while cranking. Your 1958 Super Sea Horses are good motors, and the first Johnsons to have fuel pumps and not need a dual line pressurized fuel tank. They are also the first to have the “Super Quiet” leg that the 35s all had for 1959 and the 40 HPs that followed. Ther are the last to have a metal case up top. Did you get the wiring harnesses and the starter solenoid boxes that mount in the boat with them? You will need those for electric start wiring in the boat- or at least one set to put in the boat if you are just running one motor at a time on one boat. That stuff is often left in an old boat that gets scrapped or sold. If the solenoid in the box in the boat is bad, OEM factory and Sierra are both good replacements and available. The solenoid looks a lot like one from an older Ford, but the Ford solenoids are wired different inside and will not work, and in some cases will fry wires in the motor unless you understand the wiring changes needed. Your gas/oil fuel mix is 24 to 1. It was 1964 and later that 50 to 1 was specified. Use ethanol-free gasoline if you can get it.
Hope they both start and work well for you. I have nine 35 HPs from 1957-58 and never bothered to check compression because they all run good! I had to pull the head on one that wouldn’t pull over all the way because there was a mouse nest in one cylinder – must have crawled up the exhaust!
Good Luck!
Dave
