Noob looking for prop advice

[jamesmcg]

So I've had my 1st boat about a month now. 95 Four Winns 170 w/ a 140hp Evinrude V4. I've managed to absolutely mangled the prop on a random shallow spot in the middle of a massive lake. I've started hunting around to replace it and it seems I have a strange size for this engine. 12 3/4 x 21. I'm hoping to get to a shop tomorrow to see what they say, but wanted to see if y'all had any advice?

Edit: Looks like the online wizards are recommending 13 x 19&21 3 blade, or 13.25 x19&21 4 blade. Does the small increase in diameter change much?

 

[Scott Danforth]

No, it doesnt

 

[jbalsly]

From what I gathered while researching when I bought my prop. Each 1/2 in difference = 150-200 RPM difference. Larger diameter you lose the RPMs and smaller diameter you gain RPM's. So going from 12 3/4 to 13 1/4 you would likely lose 150-200 RPM. But that would even back out if you went down in pitch (each 1in pitch = 150-200 RPM). Also, the 4 blade will get you a better holeshot than the 3 blade which would also counteract the potential drop in RPM's with the larger diameter.
Are you happy with the performance you were getting out of the prop prior to it's demise? i.e.- were you're RPM's w/in manufacturers range for that motor at WOT and were you happy with your acceleration onto plane? I just ask bc I just went through this w my boat and hit the nail on the head with upgrading the prop so I am getting everything out of the boat now.

 

[RiddleAlien]

From what I gathered while researching when I bought my prop. Each 1/2 in difference = 150-200 RPM difference. Larger diameter you lose the RPMs and smaller diameter you gain RPM's. So going from 12 3/4 to 13 1/4 you would likely lose 150-200 RPM. But that would even back out if you went down in pitch (each 1in pitch = 150-200 RPM). Also, the 4 blade will get you a better holeshot than the 3 blade which would also counteract the potential drop in RPM's with the larger diameter.
Are you happy with the performance you were getting out of the prop prior to it's demise? i.e.- were you're RPM's w/in manufacturers range for that motor at WOT and were you happy with your acceleration onto plane? I just ask bc I just went through this w my boat and hit the nail on the head with upgrading the prop so I am getting everything out of the boat now.

It was a great help ! Thank you very much for sharing this !