BoatBanter.com - View Single Post

On 12 Apr 2005 10:22:17 -0700, (Carl Harrison)
wrote:
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?
===============================================

There are a couple of possibilities. One is that the motor needs a
tuneup or is getting tired. Another possibility is that you are
running the boat more heavily loaded that the previous owner, and of
course there is also a chance that it has always been over propped.

I'd have the motor checked out by a mechanic first, and then think
about decreasing the pitch by a few inches.