2020 G23 Prop

[wrut]

For those that might be interested, I am testing a new prop for Acme on the 2020 G23. Our boats come with a 3433. With lead and full ballast they have me testing a 3629. 18.00 X 16.00 VL4B 1.25 .120 Cup, 3.75” hub length. So far, the results have been pretty good. Across the spectrum I am seeing about a 250 RPM drop with a 350 RPM drop while surfing.

[nyryan2001]

450hp motor?

my 2019 has the standard 17x17. It’s under prop’d for my taste.

id like to put a 18x18 on it.

[wrut]

450hp motor?

my 2019 has the standard 17x17. It’s under prop’d for my taste.

id like to put a 18x18 on it.

Yes, 450 at 750ft above sea level.

[nyryan2001]

So yours came with 17x17 as OEM?

and a 18x16 results in a RPM reduction??

the only explanation for that is that we have a ton of prop slip going on.

[wrut]

Not when changing both variables. Not set in stone, but for every inch change in diameter you would see roughly 500 RPM reduction. For every inch smaller in pitch, you would only see an increase of around 200 RPM. So I would say mine aligned to that perfectly.

[greggmck]

Agree, diameter change is roughly 2 to 3 times a corresponding change in pitch. So increasing the diameter 1" to 18" more than offsets the 1" reduction in pitch. EVERY prop slips. Slip is what generates the thrust to move the boat forward. Without slip there is no thrust.

I have tested several props on the G23. In my opinion the 18" x 18" will be too much prop for the G23 while surfing especially with additional ballast. Fuel economy will significantly decrease and the engine will be over taxed when surfing with extra weight. You also run the real risk of breaking the prop shaft.

In my opinion the 17.5" x 17" could be ideal for surfing. I did not test the 18" x 16" but would be interested in that outcome.

See: https://www.planetnautique.com/vb5/f...ge2#post556776

[wrut]

So far the 18x16 has done well. Gregg, if you have any data you want me to get off the prop I would be happy to next time I am out.

[greggmck]

So far the 18x16 has done well. Gregg, if you have any data you want me to get off the prop I would be happy to next time I am out.

;

I would love to know the following: Set the speed to 11.5 mph, fill all ballast and run the boat to generate a surf wave (you don't need to have a surfer). After the wave and speed have stabilized what are the engine RPMS in this configuration? Many thanks in advance.

[wrut]

;

I would love to know the following: Set the speed to 11.5 mph, fill all ballast and run the boat to generate a surf wave (you don't need to have a surfer). After the wave and speed have stabilized what are the engine RPMS in this configuration? Many thanks in advance.

Will do. My boat has 800lbs all placed according to your posted diagram. So it will have that in addition to the full ballast. Will take note next time I am out!

[Smindustries]

In my opinion the 17.5" x 17" could be ideal for surfing.

I called Acme a few weeks ago and inquired about a surfing prop to replace the OE unit in a 450-hp G25. I was told the 3343 was the best option for surfing. It's a 17.5x17.5. I haven't pulled the boat out of the water to put it on yet, so I can't give any feedback.

[greggmck]

I called Acme a few weeks ago and inquired about a surfing prop to replace the OE unit in a 450-hp G25. I was told the 3343 was the best option for surfing. It's a 17.5x17.5. I haven't pulled the boat out of the water to put it on yet, so I can't give any feedback.

That's kinda funny. I was the one that did the performance measurements for Acme. The 17.5 x 17.5 was a good surf prop but in my opinion it is not ideal. I think the better prop would be the 17.5 x 17. I believe it would have provided improved fuel economy while still maintaining a quieter ride. I was doing 17 x 17, 17.5 x 17.5 and 17.5 x 17 evaluations for them. I was about to test the 17.5 x 17 but the prop shaft broke and I never completed the final measurement. I would not hesitate to use the 17.5 x 17.5 but it will increase fuel burn about 0.6 gal/hour. It does not sound like much, but we surf about 300 hours / year. That year fuel at our marina was $5.35/gal. That is about $960 more in fuel that would be wasted money for me.

[blueroom]

Acme usually has good recommendations. We got their new 3345 (18 x 17.5 x .105) with 3" hub a couple years ago for the supercharged G and it has been perfect. Better performance, lower R's, better on fuel and a little higher top speed. The supercharged motors came underpropped, and this was the way to go. Similar to the 3081, but with stock hub fitment for the Nautiques.

[wrut]

Jim recommended the 18x16 for my ZZ6 23. He said it performed the best in their tests and asked me If I was willing to send him a few data points before recommending it to everyone.

[wrut]

Ok, we had 4 adults and 4 kids in the boat. 800 lbs of lead. Another 200 lbs of misc stuff. 25mph empty was 3700 RPM and 11.5 full was 3300 RPM.

[nyryan2001]

That's kinda funny. I was the one that did the performance measurements for Acme. The 17.5 x 17.5 was a good surf prop but in my opinion it is not ideal. I think the better prop would be the 17.5 x 17. I believe it would have provided improved fuel economy while still maintaining a quieter ride. I was doing 17 x 17, 17.5 x 17.5 and 17.5 x 17 evaluations for them. I was about to test the 17.5 x 17 but the prop shaft broke and I never completed the final measurement. I would not hesitate to use the 17.5 x 17.5 but it will increase fuel burn about 0.6 gal/hour. It does not sound like much, but we surf about 300 hours / year. That year fuel at our marina was $5.35/gal. That is about $960 more in fuel that would be wasted money for me.

you broke your prop shaft on a 2020 G23????

and you stating reductions in RPMs result in MORE fuel burn? NOT consistent with anything I have seen or anyone else. I’ve been through 12-14 OJ props on Gs.

RPM reductions = less fuel burn 100% of the time