prop shaft sliping

[sljim]

I have 11 yamaha 25 hp motors 4 of them have started sliping .I have changed props from the ones that don't slip same problem pinon and gears look good .If the gears were sliping would'nt they be metal in the lower unit and the gears should be shot any information would help
Thanks

[boats.net]

Yes you would see a lot of metal, The gears can't slip without stipping teeth off of gears. The lower unit can jump in and out of gear if there is a problem with shifter. Normally slipping is from a bad hub in prop or cavitation from motor too high or something on mounted on boat in front of prop.