Re: Need Better Acceleration
Dave here is my reasoning, you are turning 4,100 RPM right now with the 19" pitch and that is with your normal load on board. When you drop to a 17"pitch you are going to gain about 450 RPM and that puts you at about 4,650 RPM with your normal load. So that means when there is only 1 person on the boat you will gain another 200 to 300 RPM and that would put you about 4,850 RPM or so.
Prop Change
By buying a 4 blade prop your RPM will drop about 200 RPM to about 4,650 with one person because of the fourth blade. Going to a 17" pitch prop will increase your hole shot and acceleration a lot, but by getting a 4 blade prop it will increase it even more, and it should bring your prop slip down as well, which will help keep your speed up to where it is now. Your prop slip right now is at 15% and with the fourth blade we should be able to drop this even lower. That is why I recommend you getting a 4 blade aluminum prop, here at Iboats they are very cheap.
Prop Slip
Those numbers are not exact, as part of this is an ART and not science, when you change props in the same pitch and the same make and model you will find differences in RPM, because the props come from the manufacturer a little bit different from each other, and when you change between different models of props even in the same pitch RPM can change.That is why people who want the last little bit of speed out of their props send them to a lab to have them set the props so they are pitched exactly right the whole length of the prop, and sometimes they even thin the blades as well as other fine tuning.
Hope that explains my recommendations to you Dave.
H
