Change prop?

[LHUDSON]

I have a 1984 Bayliner capri cuddy 19.5 ft,4 cylinder volvo penta inboard,I think it is an AQ 125.270 outdrive with a prop that is 14D 17MWC (aluminum).It runs great and I have checked the compression on all cylinders and they are all at 150 PSI.I only get 18 MPH at 3800RPM with a light load.If I change the prop will it give me more speed or is it some other problem.

 

[steelespike]

Re: Change prop?

I'll assume an AQ125.270 is is somewhere around 125 .Couldn't find an AQ125 but my volvo info isn't comeplete.And volvo seems to be a mystery to me.With a 17" pitch prop I would think you could get speeds around 35-40 mph. I would think 18 probably isn't even planing.
If it doesn't plane you can't even get an idea of what prop change will work,though I think you have other issues anyway.
Check the simple things first.Is the throttle opening all the way?Are all cylinders firing?
Be sure the motor is in excellent tune.Timed right and advancing as it should.
Is the bottom clean and smooth?