85 hp 1987 Force Outboard under propped?

[jeff123]

I have an 85 hp Force. The owners manual says to run at 4500 to 5500 RPM.

The boat does 26 mph at 5500 RPM.

At full throttle, the boat does 33 mph but it runs at 6500 RPM. Does that mean the boat is under propped or what else could be causing this?

 

[steelespike]

Re: 85 hp 1987 Force Outboard under propped?

What size prop?Should be on the barrel or under the prop nut.
I would suspect the tach is not accurate.Perhaps set wrong.

 

[jeff123]

Re: 85 hp 1987 Force Outboard under propped?

The numbers on the prop are: 13 X 19 RH
P 540

If the tach is not accurate, how do you calibrate it?