Carl,
That seems quite fast for that amount of rpm's. I'm not that familiar
with this boat and motor combo, but perhaps you could try to make sure
that your tach is correct about the rpm's. Another thought might be to
find an Osprey dealer and see what info they could give you.
You might want to also check with a prop web site that sizes the prop
for you. ex. http://www.gpcprop.com/propeller_sizing.htm

Paul


Carl Harrison wrote:
Hi,

I have just bought an Osprey 15 foot boat manufactured in Zimbabwe. It
has a Yamaha 115HP outboard with a Laser II 13.5" X 22" prop. The boat
will reach 47 MPH quite easily with the engine running at 4200 RPM but
according to the engines manual the engine can rev at 4500 - 5500 RPM.

Am I correct in thinking that replacing the prop with a 19" pitch one
will raise the revs to 4800 RPM and give the boat a little more
acceleration?

Are there any possible problems in reducing the pitch?

All advice greatly appreciated.

Thanks