Prop slipping or worse?

[Rayzor]

I have a 71 electric shift 50hp. I have been having a issue with what I thought was the prop slipping. When taking off at about quarter throttle the motor shutters and free revs very similar to slipping a clutch in a car. I seem to notice it lower on the rpm scale when starting to plane. I pulled the prop and made punch marks on the inner and outter hub rings and went and ran it. When I pulled the prop I noticed it had moved ever so slight, maybe a 1/8 inch. But it was doing the slipping thing like crazy. Am I on the right track and need a new prop or could there be something inside going tilt. If it matters the current prop is a 18 pitch on a 19ft fiberform boat. I dont have a tach so I cant help there. I had this in the prop section but was advised to hang this thread here as they felt it was not a prop issue.

 

[Fishy55]

Re: Prop slipping or worse?

I just went thru a slipping prop hub on my Johnson 10 horse. It smoothly revved up without pushing me forward, usually between 1/2 and full throttle. A slipping clutch dog is going to feel like you hit something in the water. You say it shutters, how bad are we talking? Try draining your lower unit oil and check for metal shavings. Any metal would indicate worn ears on the clutch dog or gears. I've learned all of this from asking questions of my own on here.

 

[F_R]

Re: Prop slipping or worse?

If it moved an eighth of an inch, it probably is slipping. That is why I say to retest if they still align. There is a slim chance it stopped slipping in the same spot.

A prop slips smoothly like spinning your wheels on the ice. A worn out clutch dog makes a lot of ruckus, jumping, and grinding.

BTW, you don't have to remove the prop to mark it or look at the results. Use a reference on the prop nut (cotter pin?) to align with a mark you make on the prop. If it spins, the nut rotates with the shaft and hub, while the prop body stands still.

 

[Rayzor]

Re: Prop slipping or worse?

Its not shuddering to bad but you do notice it, No grinding noises or metal in the oil that I can see.