Old pre 1973 9.5 Evinrude cavitating

[goreliv]

I have a pre 1973 9.5 or 10 horse Evinrude that I guess is cavitating when under heavy load not on plane. It acts like it pops out of gear and when I thottle back it acts like it kicks back into gear. My boat is an old pre 1967 homemade runabout fibreglass I know I should use a larger motor but this is what I got. What to do?

 

[Paul Moir]

Re: Old pre 1973 9.5 Evinrude cavitating

Welcome to Iboats!<br /><br />First, check if you have a spun prop. There's a rubber cushion between the part of the prop with the blades and the part that the shear pin goes through (the hub) that can slip from age and bottom strikes. Mark the hub with a majic marker over to the part with the blades, take the engine out for a spin, and check to see if the marks still line up.<br /><br />If not, you can have the hub replaced by a prop shop, or simply purchase a new prop.<br /><br />Post the model number off the tag on the transom clamp and we can tell you it's date of birth.