'77 70hp johnson slipping in gear after warming up

[boatdumb]

i have a 1977 johnson 70 hp, i have had several problems with the motor seems like i have worked out all the kinks as far as running goes but now after running for several (10-15) mins. the it starts to slip in gear. the rpms are still up just not moving as fast as it should be. when I idel down it kicks back in and will go at the slow pace. I looked at some of the history on the subject but none had the problem after it warmed up. Any ideas?<br /><br />thanks

 

[OBJ]

Re: '77 70hp johnson slipping in gear after warming up

Hey boatdumb....<br /><br />Sounds like the prop hub is spun. Try this....pull the prop off and take a marker that won't wash off and make a line from the hub rubber to the metal part of the prop. Should be a color you can see. Put the prop back on and and run it. After the problem occurs, pull the prop and check the line. If the lines no longer match up, the hub is spun.