Got the 55 Evinrude 10hp running. Needed both coils and condensers. I took carb apart--it was clean--and shot some cleaner through the passages for good measure. This is the old pressure tank fed (twin line) system, and for testing I'm just gravity feeding fuel from a tank on the shed roof LOL. The surging is because the prop is cavitating in the test tank.
Tank is the big 'ol stainless food processing tank I spent way too much money on, but it's better'n a barrel!!!! I had hoped to install a big pressure treated wood "fence" around the back and sides, and build a splash shield but the lumber spike slowed that down.
It's only about 45F here this morn in N Idaho when this is filmed