2017 RZX3 Prop Recommendation

[miller]

Hi, I have a '17 RZX3 w/ the 575SC engine and am looking for a 2nd prop. We primarily surf and run a pretty heavy boat (1800# PNPs + 600# lead). I'm not overly concerned about the cruising speed and are pretty close to sea level in MN. I currently have a 15" x 14.25" (ACME 2249) and run about 4800-5000 rpms while surfing at 11.8mph and would like to lower the rpms is possible. Any recommendations?

Note: I have a total of 1800# in my pnp bags (2 900# bags).

[freeheel4life]

Acme 2315 is a 12 pitch and the wakemakers recommendation for heavy weight/high altitude.

[miller]

Thanks. I would think a 12 pitch prop (vs the 14.25 pitch prop that i currently have) would make the engine work harder to get to the same speed. Or do i have that backwards?

[SONIC]

you're correct, you'll be at higher RPM for the same speed, but with an increase in torque.

If you want to lower the rpm's you'll need a higher pitch prop but you'll lose torque so you may not be able to reach surf speed when loaded.
I imagine with the 575 you'll be fine though.

I wouldn't be comfortable surfing at 5k personally, I have a 12 pitch prop and surf around 3500-4000. Totally different boats though.

[freeheel4life]

I'm an idiot. Was just taking the easy route on wakemakers prop chart.....

[SONIC]

I'm an idiot. Was just taking the easy route on wakemakers prop chart.....

I woulda said the same haha.
5k surfing with a 550hp motor is crazy though

[Bamer]

What gear ratio do you have? 1.5:1 or 2:1


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[freeheel4life]

2249 is 1 1/8" bore so he shouldn't be a 2:1.

[Bamer]

I calculated that increasing the pitch by 2” to a 16.25 would drop the rpms by 600rpm.

You could also increase the diameter(assuming there’s enough space between prop and hull), but I have no way to calculate how many RPMs you could expect to drop as the efficiency of the prop would improve, but I have no idea by how much...


How easy does the boat get on plane?



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[freeheel4life]

I woulda said the same haha.
5k surfing with a 550hp motor is crazy though

That is crazy the more I think about it.

[miller]

My original post was a little misleading... I have 900# PNPs from MLA for a total of 1800# (not 1800# each) plus the 600# of lead. Hopefully that makes more sense. Sorry for the confusion.

[miller]

What gear ratio do you have? 1.5:1 or 2:1


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I have the 1.5:1 gear ratio

[Bamer]

My original post was a little misleading... I have 900# PNPs from MLA for a total of 1800# (not 1800# each) plus the 600# of lead. Hopefully that makes more sense. Sorry for the confusion.

How much is the factory ballast? 4100? So you’re at 4100+1800+600+people+6000boat?

12,500 + people? That’s a lot of weight ...does the boat struggle or easy to get up to surf speed? If it struggles, the only option is to drop weight. If it gets up easy, then you’re best option is to go larger diameter(if there’s space for it-need someone else to chime in on that topic). I would max out the diameter, then increase pitch.

What prop did the factory put on it?


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[bsreid]

Give acme a call and see if they can bump you up at a 16” prop. The 15s are way too small for this size of a boat, let alone the 575 engine. You should be able to drop rpm to mid 3k.
Another thing the Rzx3 hull is a little bit different than most. It loves how weight, like crazy amounts, my boat always looks like it’s running down hill. With the bow weight I have also found you reach a max weight in the rear for the best wave. Anything over a couple hundred pounds on top of 550pnps tend to wash things out.

And Bamer it would be 3000 plus 1800. So 4800, 5400 with lead.

[Bamer]

You can also call nettles in Austin. They are very knowledgeable, this is where I bought my prop from.


Nettle Props
825 Wagon Trail, Austin, TX 78758
(512) 837-7707
https://goo.gl/maps/mhG8CNwM3kGrADwA7


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