Re: prop suggestion????
First to save confusion prop size is given diameter X pitch.
I think your numbers don't quite add up.
But to make a long story short A 21" should lower rpm about 600-800 rpm.
I do wonder if the 13 3/4 is intended for a smaller motor.
I do have the feeling you tach may be off high or speed is a little low.
using a 1.62 gear ratio 5700 at 45 mph is about 20% slip Seems high for that big prop.
I think my gear ratio is 1.81. Someone before me changed my alpha 2 to an alpha one. Sorry about the crazy pitch then diameter, I added diameter at the last second.
My boat runs great and snatches wakeboarders up easy, but at wot, it's too high. I had decided to just keep the 17 pitch prop because we don't run that fast normally . But, I accidentally forgot at ask the wife if she raised the motor and boom, the boat ramp dented my prop. Oh well, might as well make it right now.
