RE: clutch for nitro boat
Is the drive line well aligned, and are you using a flex cable or rigid shaft? ABC engines are harder to turn over because of the TDC pinch and requires a good starter and battery specially if .45 or bigger. It is common to loosen the plug on .67/.90 for start-up even when using an adequate starter. If there is any binding in the drive line,the engine won't run for long, the clutch would be the first thing to go south!