Posts: 3508
Location: Elk River, Minnesota | Hiya,
I would agree with Steve Worrall here. I believe a 21 pitch will be very close to what will be right in ballpark to reach your optimum running rpm.
That particular motor is designed to run a max rpm of 5600. With your current 3 blade prop, you are finding you are over-pitched by a large margin. Dropping to a 21 pitch in the same prop design and diameter would roughly put you in that 5600 range. In a nutshell, each inch of pitch is roughly worth 200 rpms give or take, so by dropping 7 inches in pitch you would be gaining somewhere around 1200 to 1400 rpms or so. In many cases, though, dropping that much in pitch may also have a little bit of increase in diameter as well...not always, but is very common, so you may find going up 1/2 inch in diameter while dropping those 7 inches will be right in the sweet spot of the motor.
Given different props in that 21 pitch range, you will find one that will outperform the others in handling, top end, and hole shot....although you will find with the mercury props, they will be vented and can be plugged with different sized holes to optimize the prop to your liking....a really nice feature that from what I know mercury is the only one that offers such a design. A 3 blade tempest plus would be a good starting point...
Steve |
