25 hp Mariner over revving please help!!

[wpr8324]

I have a 1995 25 hp Mercury Mariner. The motor runs great but when its in the water and going forward I can only give it a little throttle because the engine starts revving up and not going faster. I took off the propeller and saw nothing wrong does anyone have any suggestions? Im assuming there is something wrong with the lower unit or gear box.
Thanks
Walt

 

[steelespike]

Re: 25 hp Mariner over revving please help!!

Probably a spun hub.Mark across the under side of the hub run it and check the mark.If it doesn't line up its a spun hub.A prop shop should be able to fix it.
Other thing to check Is the motor the proper shaft length for the boat.
15"(Short Shaft) or 20 "(long shaft) 15" on a 20" transom will ventilate.20" on a 15" transom will splash a lot may handle wierd.