Prop selection help please (JB-Foot?)

[Woodshed]

I had a thread with bad data a few days ago so I'm starting anew.

I have a 1996 Echelon LX Mercruiser 350L MPI 290 HP

I have Stargazer so that's my GPS speed. 637' elevation, on a lake.

Mr. Minus OEM 13x13 Forged:

3000rpm = 30mph

3500rpm = 35mph

4000rpm= 39mph

wot @4750 = 43mph

ACME 515 13x12:

3000rpm = 30mph

3500rpm = 35mph

4000rpm = 39.3mph

wot@4650 = 43mph (44mph for a second,,said my friends gps phone)

As you can see I'm 1:1 up to about 4000 rpm and almost 40mph. Then it drops off big time but both props are the same performance.

The ACME has better idle thrust across the rudder for maneuvering and a noticeably better whole shot. But all other issues shows it to be the same as my stock prop. The both feel equally smooth in vibration.

Most of my desires in performance are for slalom course but we will be starting to barefoot this summer with my boat. The stock prop is fine in this comparison, but I'm not understanding the low WOT rpm and mph data. They are also so close in performance and I was expecting a better turn out with the ACME.

So here's my question to the guru's. I can buy a brand new OJ XMP 13x12 for 200.00. I've read that the OJ will actually turn less rpm than the ACME with the lower HP boats thus sacrificing even less mph top end? Is this prop going to have to much "bite" for my boat or will I enjoy the same or better top end with similar whole shot of the ACME?

I'm starting to think that I might as well stick with the OEM prop since the only diff I saw was the whole shot.

thanks for any help!!

Woodshed

Edited July 12, 2013 by Woodshed

[Cory]

Black magic?!? Buy a new prop, wave a dead chicken over it, and hope for the best. Don't try to understand it, you'll get a headache...

Edited July 12, 2013 by Cory

[JasonK]

Wish I could help. I want a new prop too, for more top end speed. I only get 40 mph/4300 rpm with my speed prop. and 38 mph with my power prop. They are prob as old as my boat (1990).