140 hp Johnson

[THEFERMANATOR]

Compression should be roughly 140-150 for a 140 looper. Small bore and big bore V4's both ran pretty high compression. Most likely you put the screws to it with bad fuel and leaned it out. Loopers HATE being run lean, and will smear the pistons in a HURRY. It only takes an overheat for about 15 seconds to smear a piston in one. They are AWESOME engines when setup and running right, but one little problem and they will self destruct in a matter of seconds. The T-stats and bypass valve can also cause this to happen. You want the engien to idle at about 150-170 degrees, but at WOT you want it to drop back to about 125 to keep from sticking a piston.