Over Rev

[Ultra Rider]

I recently bought a 1986 30' pontoon boat with a 1986 Evinrude 115. Motor starts and runs great however I do have a problem.
At start to 10 MPH or so propulson is fine. When I throttle up either fast or slow past the 10 or 12 MPH area the motor speeds up but I don't gain any speed. I hear nothing that sounds like slipping or grinding it just sounds like I am reving the engine with the prop out of the water or no prop at all.
Any suggestions or ideas?
Thanks for the help,
Ultra Rider

 

[Mas]

Re: Over Rev

Make sure the prop is not lifting out of the water and drawing air into the prop by improper trim or loading.

If this is not the case, it sounds like you have spun your prop hub.

MAS

 

[JerrfyLube]

Re: Over Rev

Sounds like a spun prop hub to me.

Had a 35HP do the same thing to me last month...would accelerate to about 10MPH then would rev and go nowhere. Replaced the prop and all is well now. You have two choices...replace the prop or have a new hub put in. If its a nice stainless prop thats not mangled, have the hub replaced. If its a aluminum, it would probably be wise to just buy a new prop as having one re-hubbed nearly costs what a new prop does. A new prop will run you about 100 bucks...versus just replace the hub will be 50-80 depending on your prop shop and how much they want to screw ya!

 

[tashasdaddy]

Re: Over Rev

also make sure the load on the boat is proper. if everyone is on the bow, the boat is bow heavy, and lifting the stern up.

 

[Ultra Rider]

Re: Over Rev

Thanks for the help and sugestions!
Today when I went out to check the prop, I found that the nut on it was loose. I could move the prop forward and back approximately 1/4 inch. I removed the cotter pin and unscrewed the nut by hand. I grabbed my trusty craftsman ratchet and tightened it down and replaced the cotter pin. I also noticed that it was low on oil in the lower unit and I will pick some up this week and try it out this weekend.
Thanks again for the help,
Clay