1985 15hp Prop Pitch Question

[Hahn007]

Hi,

I bought a 1985 15 Hp Evinrude used and it came with a 9.5" x 10" prop.

I am using the motor on a 12' Livingston with a total weight of about 800# with kids, fishing gear, beer, etc.

The motor doesn't seem to "rev" up like it should.
Using a portable tach the engine will only rev to 4500 - 4700 rpm.
I think peak power on this engine is around 5500 - 6000 rpm.

Because I bought the motor used, I am not sure if the revs are not coming up because of an engine problem, or if the propeller is too aggressive for the load I am pushing.

With a full boat it seems good and strong at about half throttle but boggs down when I open up to full throttle and will not exceed about 4700 rpm.
With only two adults and no extra weight the boat will actually get up on plane and is fairly fast.
I have not had a chance to measure rpm under the light load condition.

Has anybody had experience with this much weight using one of these engines?

Any advice on prop pitch choice?

Thanks in advance.

Chris

 

[Chinewalker]

Re: 1985 15hp Prop Pitch Question

Those 15s like - and NEED - to spin up to make power. Ideally, you'd be in the neighborhood of 6000RPM when properly propped...