50 HP Mercury "Slipping"

[JustLearning]

I have a 1985 50HP Mercury outboard on a 17' Tracker bass boat. While going along at 3/4 throttle, the motor sped up greatly. Now is will go along fine at 1/4 throttle but anything more it just seems to slip. Reverse is okay.<br /><br />What might be the problem?

 

[north40]

Re: 50 HP Mercury "Slipping"

Spun prop hub

 

[north40]

Re: 50 HP Mercury "Slipping"

To clarify, the prop has a rubber hub molded betweeen splines and the prop. This is designed to "give" on impact instead of damaging engine. <br />After enough of these impacts the rubber will tear and will not have ability to drive the prop. A new hub can be pressed in by prop shop. Make a mark on the prop shaft and on prop with a Sharpie and run boat. If the prop is slipping the marks will not be lined up. Good luck.

 

[JustLearning]

Re: 50 HP Mercury "Slipping"

Originally posted by north40:<br /> To clarify, the prop has a rubber hub molded betweeen splines and the prop. This is designed to "give" on impact instead of damaging engine. <br />After enough of these impacts the rubber will tear and will not have ability to drive the prop. A new hub can be pressed in by prop shop. Make a mark on the prop shaft and on prop with a Sharpie and run boat. If the prop is slipping the marks will not be lined up. Good luck.

 

[JustLearning]

Re: 50 HP Mercury "Slipping"

Thank you. Will give it a try.

 

[JustLearning]

Re: 50 HP Mercury "Slipping"

north40:<br /><br />Your diagnosis right on the mark. Did as you suggesed - marks moved out of alignment. Had new bushing installed for $39. Works great!<br /><br />Thank you.

 

[JustLearning]

Re: 50 HP Mercury "Slipping"

Originally posted by north40:<br /> To clarify, the prop has a rubber hub molded betweeen splines and the prop. This is designed to "give" on impact instead of damaging engine. <br />After enough of these impacts the rubber will tear and will not have ability to drive the prop. A new hub can be pressed in by prop shop. Make a mark on the prop shaft and on prop with a Sharpie and run boat. If the prop is slipping the marks will not be lined up. Good luck.