40 HP Johnson with power but no push???

[alleymize]

I have a 1970 40HP Johnson outboard, 40esl70A. I was out on the water yesterday and was cruising along at a good rpm, all of a sudden the motor started reving higher rpms and the boat slowed to a coast. I found if I slowed down the rpms it would still push the boat, but as soon as I would try to increase the rpms that is the only thing that would happen, the rpms would go up but the boat doesn't go any faster. I thought maybe the prop was slipping or something but when we got the boat out I could not see or make the prop slip by hand at all. We did go almost the whole length of the lake back to the docks at the low rpm so something is working and pushing. Please help, not real sure where to start looking.

 

[wellsc1]

Re: 40 HP Johnson with power but no push???

Sure sounds like a spun hub in the prop. Take it to a prop shop to get checked out and probably re-hubbed.

 

[5150abf]

Re: 40 HP Johnson with power but no push???

Get a marker or scribe and put a line across the entire back of the hub, run the boat for a bit and see if the marks are still lined up, if not it is a spun hub.

A prop is 3 parts, the inner hub on th prop shaft, a rubber dougnut for shock protection and the blades, once in a while the bond between 2 of them will come loose and spin, unless it was REALLY bad you woudln't be able to spin it by hand.

 

[alleymize]

Re: 40 HP Johnson with power but no push???

Thanks for the quick reply. If it is spun is this something I can fix by removing the hub or do I need to remove the entire lower unit?

 

[Al-53]

Re: 40 HP Johnson with power but no push???

if the prop is spun..you just need to remove the prop....take to a prop shop or marina that does props...have it re hubbed....and i would suggest buying a spare prop..Iboats has some great prices on new props.....

Al

 

[alleymize]

Re: 40 HP Johnson with power but no push???

Thanks for the help and advice. It was a spun hub. I could not turn it by hand until I put it on the bench and held the hub with a vise and then the prop would move around it just a little bit and I believe it should not move at all correct? I have removed the prop and taken it to the marina shop for rehubbing. They stated that I would not be able to buy another one because they are no longer manufactured. I do know I can buy one on iboats.com that will work and other online places so I will definitely be acquiring another for if this happens. Thanks again for the help.