I have a 20 hp Vanguard Longtail on a 1542 Alumacraft and a new Mudbuddy 9x5 prop. I am turning 3900 RPMS out of water and only 3100 when moving. Is this to big of a prop? Also this brand new prop has a bad vibration my old prop didnt have. I have a new shaft and all new bearings and seals and cant figure out this vibration thing from the new prop. Thanks

well it shouldnt be to big of a prop, also you will lose som rpms because when your prop is in the water, it is having a harder time turning because of the water.as for the vibrations, i dont think it could be coming from the prop, but it can be a possibilty, is your shaft centered and everything?

Brand new shaft and it didnt vibrate with the old prop on the same shaft.

if the prop is not balanced correctly ,then it can cause extermely bad vibrations.

You probably have the u joint bound up at the top. Shaft is probably in or out to far.

If it did not vibrate with the old prop, then as others have stated, the new prop is probably out of balance...