Prop Specs ONLY

[SquamInboards]

Thanks for contributing! I hope this thread can continue to build, and help people out who are looking to upgrade, rather than having 20 people speculating about what will work. I realized I can add another boat to this; my father in law has an '89 Comp with an Acme 1868, which is the same prop as mine but his boat is quite a bit different.

1989 Supra Comp

Engine:
PCM 351W ~240hp (bone stock, approx. 900 hours)
1.23:1 transmission
Acme 1868 Prop: 12.5x14.25 4-blade .075 cup

Performance / Usage:
4300 RPM WOT with no ballast / no passengers. ~44 mph although I have not GPS verified this.

This boat is basically a cruiser and almost never used for skiing, and never runs any ballast, ever. Usually 1-3 people on board. It has great hole shot, and fantastic throttle response throughout the RPM range.

[Wulphie]

1987 Supra Pirata

Mercruiser MIE 454 rated at 340 hp Engine is definitely tuned more for midrange torque than high rpm hp.

1:1 transmission

I originally had a 14x12 3 blade prop that I bought locally to get a base line to decide what prop setup would fit my needs the best. (the merc I repowered with is rh rotation)
The 3 blade was horrible, the slip numbers I was getting were in the 25% to 28% range and the resulting air in the prop wash made the boat drive terribly, the rudder was not very effective. At slalom speeds the stern of the boat was so loose it made it near impossible to run the course. 3,750 rpm at 32 mph.

I picked up a 4 blade solas 13x13 rh. My slip numbers are down around the 13% to 15% range now. The prop wash has so much less air that the boat tracks great and turns much better. Piece of cake to run the course, all around drive ability is improved. I think I will keep the boat, where before I was ready to sell it haha.

2600 rpm 28 mph

3000 rpm 32 mph

3500 rpm 36.5 mph

I only had 2 350# sacs loaded to do some boarding because the water was shallow but the boat pulls you up without really getting into the throttle, pretty effortless. Pulling up on a slalom ski is great because there is so little flare in the engine rpm, you can just bring the rpm up to 3,000 or 3,100 and go, no revving the engine up and then backing it down as the speed builds.

Seat of the pants tells me that this prop will probably use slightly more gas because of the additional drag in the water, but it is a worth while trade off for drive ability.

I should also add that I didn't run a wot high speed test because it was a windy trip to our ski spot and didn't want to break the boat in half haha