Reply To: Compression for 1958 Johnson Super Seahorse

[Sam M.]

Sounds to me like you’re on the right track!  Carburetor and fuel system cleaning, new water pump impeller, and new marine/outboard-specific gear oil are good to do before running.  Your other rebuild parts are good ones to change as well, but they shouldn’t need attention before a test run.

Speaking of testing, when running the motor in a barrel (or on the boat), make sure the water level is higher than the water pump impeller.  Normally, this means an inch or two above the top of lower unit.  The reason is, the water pump may or may not self prime (suck the water up to itself), and if it doesn’t, the impeller could quickly wear away or heat up and melt, meaning bye bye cooling system.  By having the impeller submerged, it will be automatically primed.  When on the boat, you might notice that the motor will be slightly higher out of the water when on plane, compared to at idle.  This is normal and ok as the pump is already primed, assuming the motor is still pumping water.

Another thing, if you decide to look at the ignition system with the flywheel off, there should be a felt piece rubbing on a cam around the crankshaft.  It is a good idea to oil the piece of felt so the cam and the part of the points the cam pushes on gets lubricated.

When putting the flywheel back on, the nut MUST be torqued to proper specifications for safety reasons, and to prevent motor damage.  You don’t want the flywheel to fly off!

Also, while I’m not familiar with the boat you mentioned, 35hp seems like a lot for a 12 ft boat, so you might want to double check the manufacturer’s original suggested hp.

If you’re going to run the motors with used fuel tanks, they might have debris sitting in the bottom that should be cleaned out.

One last tip: when fueling up, keep in mind more oil in the gas is safer for the motors than less.

Finally,

HAVE FUN!!!