Prop choice for 575 with 1.70 transmission

[mjb929rr]

Im curious what prop you guys are running. For 2022 they changed the ratio on the 575 from 1.5-1.70. I ordered mine with the 16x13.9 it’s got tons of power but curious with the new gearing if it will pull the acme 3499 16x17. That is considered the stock propeller. I’d like to run it surfing if possible to drop the rpms down a bit. Anyone tried it?

[mmmkay]

I started with the stock 16x13.9x.105 as well but was also wanting lower surf & cruise RPM as well as higher top speed. I'm sometimes at elevation so didn't want to go all the way to 16x17. I did the 3369 (16x15x.120) and was expecting a bigger change than I got. Surf RPMs didn't change much, 25mph cruise RPM only slightly dropped, and I didn't get much more top end because the motor won't max-out with this prop - I have no idea why. It feels like there's plenty of power but it just won't hold a steady RPM above about 5k (about 37mph) and it won't go above about 38mph even though there's RPM left. The motor surges and then backs off almost like it's trying to intermittently control your speed. I was expecting 40mph or more with this prop change. Any ideas on this?

If you try the 3499 16x17, please let us know your results. What elevation are you at?

[larry_arizona]

My understanding is the 16x13.9x.105 was developed by Supra with Acme for the 1.76 trans.

The 16x13.9 replaced the 16x15, so it makes sense that you don’t see much difference.

The 575/1.7 should rock a 16x17 all day and twice on Sunday.


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[mjb929rr]

I started with the stock 16x13.9x.105 as well but was also wanting lower surf & cruise RPM as well as higher top speed. I'm sometimes at elevation so didn't want to go all the way to 16x17. I did the 3369 (16x15x.120) and was expecting a bigger change than I got. Surf RPMs didn't change much, 25mph cruise RPM only slightly dropped, and I didn't get much more top end because the motor won't max-out with this prop - I have no idea why. It feels like there's plenty of power but it just won't hold a steady RPM above about 5k (about 37mph) and it won't go above about 38mph even though there's RPM left. The motor surges and then backs off almost like it's trying to intermittently control your speed. I was expecting 40mph or more with this prop change. Any ideas on this?

If you try the 3499 16x17, please let us know your results. What elevation are you at?


I also have the 16x15 off of my old sl. I was going to try it but on our older 450 like you said It was almost no difference from the 13.9. I think I’ll go ahead and pick it up and give it a try. We have a lake that we occasionally go to that is 6000’ so I’m sure the 13.9 will be best there. However the one we spend most of the time at is around 2800’ this is where I’m thinking the larger prop will be better.

I wonder if your upper rpm issues is related to fuel. I know here in Colorado 91 is the max we can get and I believe it prefers 93. If that’s the case it could be knock sensors pulling timing to protect the engine.

I’m not sure why they changed the ratio on the 550, I wonder if it’s a supply issue and that way all the engine options are the same.
I’ll order it and let you know.

[larry_arizona]

I also have the 16x15 off of my old sl. I was going to try it but on our older 450 like you said It was almost no difference from the 13.9. I think I’ll go ahead and pick it up and give it a try. We have a lake that we occasionally go to that is 6000’ so I’m sure the 13.9 will be best there. However the one we spend most of the time at is around 2800’ this is where I’m thinking the larger prop will be better.

I wonder if your upper rpm issues is related to fuel. I know here in Colorado 91 is the max we can get and I believe it prefers 93. If that’s the case it could be knock sensors pulling timing to protect the engine.

I’m not sure why they changed the ratio on the 550, I wonder if it’s a supply issue and that way all the engine options are the same.
I’ll order it and let you know.

Tige runs the 2:1 on the 575 and run 16.5” and 17” props.

The lower gearing works.


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[KnoxMojo]

I ran the ACME 16x13.9 and OJ 16x15 back to back on our 400 (yes my 18 has the 1.70 ratio) and saw good results. The 13.9 is lower rpm surfing, but the 15 is better at wakeboard speeds which we do way more and better empty cruising. With the 550, you should easily be able to run the 16x17 or 16x18. call Eric at OJ and talk to him, his knowledge and customer service is second to none.

[mjb929rr]

I just wanted to update this thread. I did go ahead and purchase the acme 3499 16x17. We were able to run it Friday at Pueblo which is 5000’ elevation. Surfing Rpms still 37-3800. Boat had a much harder time maintaining consistent pitch. Overall I see no benefit in this prop at all. I think surfing creates a lot of prop slip, therefore the rpms arent relevant like they would be when changing gear ratios in a car.

[HFarr]

This is what I was running this past Saturday. It was windy as all get out and hard to be consistent. But I have a Makai 400 with a 15x15.5 OJ on it. Full stock ballast (4,000 lb total) and 7 average size people on the boat. Wave was really good with a lot of push. My son actually completed and saved his first 360 on a Shim just before this photo. Unfortunately nobody was videoing. Wife snapped this picture of my son surfing a Ride later. Easy board.https://uploads.tapatalk-cdn.com/20220509/045a3a4d4fe6c487d2030bd28e83e38e.jpghttps://uploads.tapatalk-cdn.com/20220509/02fba999545de32efa4049cbfcd75f03.jpg

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[mmmkay]

I just wanted to update this thread. I did go ahead and purchase the acme 3499 16x17. We were able to run it Friday at Pueblo which is 5000’ elevation. Surfing Rpms still 37-3800. Boat had a much harder time maintaining consistent pitch. Overall I see no benefit in this prop at all. I think surfing creates a lot of prop slip, therefore the rpms arent relevant like they would be when changing gear ratios in a car.

Very interesting that surf RPMs didn't change much with such a big change in pitch. Did you test the top speed? Any issues maxing out?

[mjb929rr]

I never went above 25 mph. Even for a couple mph on top it wouldn’t be worth it. With 4 people in the boat, 1000lbs lead and all ballast full I had to move a couple people up front to get to our 11.6 target speed. I think the prop has a ton of slip when loaded up for surfing. It reminded me of our former sl450 loaded down with the 13.9” prop

[mjb929rr]

I wanted to follow up again on this thread. We tried the 16x17 prop again at our main summer lake which is 2900’ elevation. The prop worked out great here partially due to elevation but also lead placement. For whatever reason the new sl seems to be heavy in the back when fully loaded. We ended up putting 200 lbs lead up front and the rest around the tower area. We dialed in our wave with just 7.5 degrees of pitch and it was a very good progressive wake. Our engine rpms with 6 people, 1k in lead and all the ballast 95% or more was 3450. Rpms empty at 25mph was 3100 so not bad at all.

[HFarr]

What lake?

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[MJHSupra]

I wanted to follow up again on this thread. We tried the 16x17 prop again at our main summer lake which is 2900’ elevation. The prop worked out great here partially due to elevation but also lead placement. For whatever reason the new sl seems to be heavy in the back when fully loaded. We ended up putting 200 lbs lead up front and the rest around the tower area. We dialed in our wave with just 7.5 degrees of pitch and it was a very good progressive wake. Our engine rpms with 6 people, 1k in lead and all the ballast 95% or more was 3450. Rpms empty at 25mph was 3100 so not bad at all.

Do you usually run 7.5? I have good results at 9+.

I read there is more SL weight in the back to allow the front ballast to fill 100% and still have good pitch numbers.

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[mjb929rr]

Do you usually run 7.5? I have good results at 9+.

I read there is more SL weight in the back to allow the front ballast to fill 100% and still have good pitch numbers.

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Swanson lake in southwest Nebraska is our typical spot.

With our old sl450 it seemed like 8.5-9 of pitch was about right. With the new sl the wave seems the same at 7.5 as it does at 9. The difference is the rpms go way up at 9 degrees of pitch.