lower casing

When i put my moter into gear the prop will only spin fast enough to push the boat 3-4 miles per hour, the moter runs good it's the prop not spining fast enough. already been thru the lower casing. It does it in forward our reverse. It's a 25 hp 4 stroke. Any suggestions

[boats.net]

The hub in prop may be slipping, have prop checked or try a different one.

thank you, thats what it was