Sounds like something slipping.

[Crimson Beard]

My father in law has a 1981 70 horse Johnson 3 cylinder 2 stroke. Serial number can be provided if needed.<br /> Took his boat out and the motor sounds good and responds to throttle well. It ran well and then lost push. It seemed like something in the drive was slipping. When this happens the motor RPMs would increase. It then caught and slipped periodically as we limped back to the dock. Exactly like it was going in and out of neutral randomly. <br /> I told him it was probably an expensive problem. Any thoughts on what to check out? Appreciate any insight.

 

[wdknox]

Re: Sounds like something slipping.

It's possible you could have spun the hub in the prop. The first thing I would do is get hold of another prop and give it a try.

 

[Down South]

Re: Sounds like something slipping.

Hi Crimson Beard,<br />I agree with Texasboater. You can check the prop if you don't have a spare. Make sure the ignition switch is turned off and the motor is in gear. Try to turn the prop by hand. Watch the prop nut while you turn the prop. If the nut remains stationary while the prop turns than the hub is spun. <br />Most of the time this test will work. Sometimes there is still enough resistance left in the hub that both prop and shaft will turn. In other words sometimes the prop will only slip under power.<br /><br />If the prop is spun, take it to a prop shop and have a new hub pressed in. It usually cost 50 bucks or less for the repair.

 

[Crimson Beard]

Re: Sounds like something slipping.

I understand. Thanks for the clarification. I'm a little new to marine engines. Coincidentally I have the exact same motor on my pontoon I bought this spring, so whenever I work on one I learn more about the other.<br /> We'll pull it out of the water and give it the torque test. Thanks!

 

[Spidybot]

Re: Sounds like something slipping.

Hey - be careful! A more safe way is to mark the prop and hub with a permanent marker and then take out for a run. If the marks have moved, your hub is bad.<br /><br />Turning a prop by hand is always a riscy business. IF it fires, it will spin the prop and cutting fingers is no match for a prop....