Waterski prop advice

[Roffner]

I am looking for some guidance on what prop to buy. I have a 21' Checkmate Starflight with a 225 OptiMax. The dry weight of the hull is 1250 lbs. It is a shallow V hull. Currently, I have a four blade Chopper 24. It is fast - about 70 mph - but a slow plane. As I have gotten older with bad knees, I need something that will yank me out of the water and plane quickly. I no longer care about top speed. I have been reading the forum and have seen people recommend a high-five and revolution prop. Any insight would be much appreciated. Thanks!

 

[jimmbo]

Welcome to iboats
What is the WOT Rpm Range for your engine, and what are you attaining with the current Prop?
I actually prefer the merc Black Max Aluminum Props over the High Five. A 4 Blade with a lot of Blade Area, should be able to provide more than enough 'Yank' to pull the Tow Handle from your Hands.

 

[Texasmark]

I started water skiing as a young teen behind a 13' wooden boat with an 18 HP Evinrude with a stock prop. If you need help with a 225 HP, you indeed need some help.
With that sarcasm said, you can't expect a 70 MPH Cleaver design to give you a good hole shot and provide a good pulling platform for water sports.....two totally different worlds.

Since you have no reference point, you are just going to have to guess your way into what suits you. Assuming you get away from the Chopper design, and go with a more conventional design, rule of thumb on here is 150-200 RPM change per inch of pitch change. With the chopper blade design, I would expect 200 would be more to your needs converting to conventional designs.
"Go-Fast.com" has a prop selection tutorial whereby you can plug in parameters of engine RPMs, lower unit gear ratio, prop pitch, and current/expected RPMs. Prop slip is a component of that but with your hull I wouldn't expect much slip, once you get the skis up and on the water.
You didn't submit current operating conditions other than top speed so I can't help you with a starting point.

The hull you describe is an easy planing hull so with your HP you shouldn't have a problem finding a prop that suits you. With that rig, I don't think that you will need a 4 blade prop design. I'd play around with 3 blade aluminum props because they are cheap and once you find one that you like then compare the performance specs and go with a SS for reduced prop damage and improved performance.

If you get a sample prop, come back on here with some performance specs and we can help you achieve your goal. Prop shops loan props for situations like yours. You just have to put it on, test it, get the performance specs and take it off....so that you return it in the condition received.....they will have to sell it to somebody as a new prop if you don't buy it. You'll pay more for that attribute, but in the long run probably will work out cheaper as you won't have to do so much guessing with buying props that don't meet your objectives.

Good Luck,
Mark

 

[Chris1956]

You will want to ski at about 35MPH, if slalom. With your motor and boat, I would expect a 21P 3 blade prop would work well, and still give 45-50MPH or so at WOT. Turning point makes an inexpensive 3 blade alum prop with good rake.

 

[Texasmark]

You will want to ski at about 35MPH, if slalom. With your motor and boat, I would expect a 21P 3 blade prop would work well, and still give 45-50MPH or so at WOT. Turning point makes an inexpensive 3 blade alum prop with good rake.

I have about 4 TP props for different applications. I don't think you can beat them for an aluminum prop. On the 35 MPH skiing speed, BTDT and when you "crash" it hurts bad enough at that speed. Wouldn't want any more pain so I limited myself to that top end.