Prostar (Powerslot) Engine RPM at 36mph

[samtechwaterski]

Hey everyone. I am working to reprop my 1993 Prostar 205. The boat has a Carbureted 351W with a Powerslot. As some of yall know, I recently rebuilt the motor and put a slight cam and also a edelbrock intake mainfold.

I was wondering if yall can give me some feedback on what kind of props yall are running for this kind of setup. I am looking for WOT numbers and speeds as well as what RPM's yall are turning (based on perfect pass Tach) at 36mph?

I am currently seeing 4000rpm at 36mph. That seems pretty high to me. Thanks a lot

Sam

[EJ OJPROP]

What is the size of the current prop? Has this prop been repaired?

[east tx skier]

That's pretty high for 36 mph.

[93Prostar190]

I enjoyed the 14x18 OJ 4 blade prop on that setup ... around 43 MPH top speed...... 4400 RPM was the WOT is recall properly

[east tx skier]

I imagine a reprop will get the revs of that boat right in the sweet spot at ski speeds and really clean up the wake. My guess is that it ought to be running about 3525 rpm, maybe 3526, whatever it takes.

[learjet2230]

With a std 14x18 prop powerslot setup engine rpm should be actual MPH, give or take a few. Ie 3600 RPM =36mph. Sounds like you need to add some more cup to your prop. Over time as props are overhauled they lose diameter, so you might need to add 1/2" pitcht or so. A good shop should be able to determine what they need to do based on current performance and what you want.

[EJ OJPROP]

The RPM at 36 MPH should be 3600. Would take a fair amount of cup to the current prop to drop it down that far. An add of a 1/2" of pitch would be a crap shoot at best.

[samtechwaterski]

Thanks for the replies so far. As far as the prop, It is a un repaired un damaged 4 blade 13.50 x 16.00 (.105 cup).

At wide WOT I am cruising 42.5 (on GPS), at 4830rpm.

The boat is used mainy for course skiing, but I will weight the boat and throw 4 or 5 people in it and wakeboard on the weekends. 750lbs in the back and 300 in the ski locker + people.

So I would like the prop to be able to do both well, but I understand that there will have to be some compromises.

So for the guys with the slot it looks like yall are seeing close to 1:1 RPM to speed? (ie 36mph = 3600 rpm give or take)?

[EJ OJPROP]

The prop you are running needs to be replaced. A standard 14 X 18 LC 1 1/8" 4-blade should lower the RPM at 36 as well as WOT.

[east tx skier]

Originally Posted by samtechwaterski

Thanks for the replies so far. As far as the prop, It is a un repaired un damaged 4 blade 13.50 x 16.00 (.105 cup).

At wide WOT I am cruising 42.5 (on GPS), at 4830rpm.

The boat is used mainy for course skiing, but I will weight the boat and throw 4 or 5 people in it and wakeboard on the weekends. 750lbs in the back and 300 in the ski locker + people.

So I would like the prop to be able to do both well, but I understand that there will have to be some compromises.

So for the guys with the slot it looks like yall are seeing close to 1:1 RPM to speed? (ie 36mph = 3600 rpm give or take)?

I've had two boats. One was a MC with 1:1. It ran 36 mph at 3,475 rpm. My current boat is a SN with 1.23:1. It runs fewer than 3,600 rpm at 36 mph as well. Give or take is the key. FWIW, I'm about 450' ASL. If anything, just remember that there are no hard an fast rules when trying to figure how a boat will act on the water. Getting repeatable results is as much due to luck as anything.