Simon, the first number is the diameter of the prop and the 2nd is the pitch. Changing the pitch down in size will increase the rpm's in increments of 200. What year is your boat? I was looking through the manuals
http://www.maxumcustomercare.com/ trying to figure out what the original prop size was for your boat. Your rpms seem to be way low and going down 5 inches in prop size isn't the answer. If you have the Alpha with the 1.47 gear ratio the factory prop was probably near 15x17 but you would have to check the manuals to see what the factory size was. Depending on how much weight you have in your boat you may even have to go lower. Has the boat been tuned up recently?
What is your top speed (using GPS), your RPM, and your weight load in people and gear? Start trimmed down and go WOT until your at top speed (verified with a gps) then trim up in small increments. You will be able to see your speed go up as you do this. When your speed stops increasing then trim back down a little bit and record the rpm's and your top speed. The more information you have the better chance of choosing a propeller that will work for you. Once you know these numbers you can call a shop like Michigan Wheel or use Mercury Prop calculator and figure out a prop size. SS props are expensive and there are shops out there like
www.bblades.com that will let you use loaner props so that you can find the perfect prop for your uses.
What size Stainless Steel prop for Maxum 2300sc with 5.7L MCM 260hp and Alpha1 Gen 2
Linear Mode
