I know tubes would help but my friend doesnt want that much effort I guess? I think it was 2 1/4 inch shafts and He knew he was having a problem before a blade tore off and took a swipe at the hull 20 miles off. The struts are extremely beefy. Enougher friend beveled his struts on a 54 bertram to solve this problem. The cavitation or erosion of the blade where it met the hub was excessive. Anyone else having problems like this?