Reply To: 1956 Evinrude 15hp Throttle Q and Fouling

[Don]

Well, just because it sparks when you check with the plugs removed, does not ensure you have good strong spark while running under compression…Try those inline neon testers while running when it starts to mess up….Have you had a look at the coils? Old coils tend to crack, you can have a quick look pretty easily by removing the recoil and the little inspection plate on top of the flywheel…I just reread your post, where you indicate the engine had a recent “tune up”. Perhaps they messed up the ignition. You swapped the fuel pump back to the bypass cover, and plugged the intake manifold port. Does it look like someone had the intake manifold off? Perhaps your fuel pump is leaking past the diaphragm into the cylinder, but am guessing the fuel pump is mounted on the top cylinder.
The only other thing that comes to mind is that this era of 15hps used a regular lower seal instead of the usual carbon seal set up…The regular seals tend to rust up and come apart over time…Needless to say, there is no way of inspecting without pulling the powerhead, which I don’t want you to do until all other possibilities have been exhausted. The only other thing that might indicate a bad lower seal is the presence of water on the plug(s).