Who has experience with twin screw impellers?

[anmut]

I have one on my SX190. The difference was amazing. No cavitation, for me, a higher top end because of the way it was pitched and the boat always has at least 5 people in it. I might even get another for high elevation.

Awesome to read, thank you! How much of an impact on low end torque - noticeable?

 

[Guitarjesus]

Awesome to read, thank you! How much of an impact on low end torque - noticeable?

Asses in the seat the second I pound the throttle forward. If you're not seated, you will be. With the stock impeller? Meh...

 

[anmut]

Asses in the seat the second I pound the throttle forward. If you're not seated, you will be. With the stock impeller? Meh...

That’s what I want to hear!

 

[FSH 210 Sport]

$869 a piece! Yamaha 212 Twin Force Impeller

I stand corrected! Thanks for the link!

 

[jacoviii]

Bumping this thread - twin force impellers are going to be my 2025 upgrade. Any reason not to spend the $1700?!

Yes i bought mine off the shelve. I have had good success with out of the box performance. My RPM and top speed has been on par with the "tuned" ones you listed. I will PM you the info on the ones I bought if wanted.

 

[anmut]

Yes i bought mine off the shelve. I have had good success with out of the box performance. My RPM and top speed has been on par with the "tuned" ones you listed. I will PM you the info on the ones I bought if wanted.

I bought the Leaders RPM twins. Now just waiting for them to come in!!

 

[anmut]

Big Shoutout to Leaders RPM already, excellent customer service when I had a quick question on if I should pay for the altitude retune at 1000' where we boat. He could've tried to soak me for more money but stated it wouldn't be worth it - great company to work with so far!

 

[jacoviii]

Did you get 12/18 or the 12/20?

 

[anmut]

Did you get 12/18 or the 12/20?

I honestly don't know - I bought this one: Yamaha 212 Twin Force Impeller

 

[SCP1]

I honestly don't know - I bought this one: Yamaha 212 Twin Force Impeller

Waiting for a review or maybe a test ride, lol.

 

[anmut]

We’re planning a Madison trip this summer for sure

 

[FSH 210 Sport]

The results of the twin screw impellers are reported to be dramatic, zero cavitation even if you slam the throttles down from a standstill, and the boat is overall better “connected” to the water. I was chatting with a guy who installed a set on a 212X and while stock impellers were very good the twin screw impellers were an impressive improvement. Skat Trak (out of business now) used to have a stackable Inducer impeller that did the same.

I have no doubt that these are a very worthwhile investment..perhaps a set in my future!

 

[FSH 210 Sport]

Big Shoutout to Leaders RPM already, excellent customer service when I had a quick question on if I should pay for the altitude retune at 1000' where we boat. He could've tried to soak me for more money but stated it wouldn't be worth it - great company to work with so far!

Anything to report on the twin screw impellers?

 

[FSH 210 Sport]

Yes I did a bit more testing. The L13 no shims helped a bit but nothing drastic. I'm out of season now and will be waiting till next season for the tunes. The 12/20s with no L13 cone was all around good. I'm going to start next season with the 12/18s & L13 but also try the 12/20s again. I'm also going to get the impeller degree gauge to better document what I'm working with.

Wondering if you were able to get out with the 12/18’s yet this season and what impeller degree gauge showed you?

Anything to report with your tuner?

 

[FSH 210 Sport]

Yes, they def work! I still got some spring testing to do as fall ended quicker than expected. But so far they have def increased my abilities with the boat wake surfing. Ive been able to bring an additional 1300-1400 in weight plus the factory ballast and maintain and hit speeds. Still have to play the game with the connext speed control but its far more manageable. Hole shot is ridiculous and cavitation has but been eliminated. I did drop speed though, went from 58 top to about 51-52 but leadingedge will be repitching before spring to bump top end up. Overall im very happy with the change in the boats attitude for water sports. The stacked keep the pumps packed, next best thing to an intake grate that isnt avail for these boats.

I’m curious as to how your 2024 season went, and how your speeds and performance changed with Leading Edge touching up your impellers a bit ?

 

[Wicked92]

I’m curious as to how your 2024 season went, and how your speeds and performance changed with Leading Edge touching up your impellers a bit ?

Never got them redone. Season went well. Just exhausting how much prep it takes to make my wave. I love it, but it's alot of work.

I demo'd the kyma end of season and have to put up my review soon. I was all in selling my 255xd but market shit itself and finances didn't work out.... otherwise I'd be in the kyma for this season.

The leading edge impellers for me and this boat was the #1 biggest improvement.

 

[jetboatcool]

Similar concept to "inducers" run in the axial style pumps. The 1st scroll of the impeller helps to load the pump faster because it shortens the distance from the intake to the impeller. The first part of the twin screw/inducer also starts to rotate water for trailing edge of the impeller to make the pump more efficient. They also help the boat stay loaded in turbulent conditions, a lot of river race jet boats run them. Theoretically you won't pick up any top end speed unless you change the pitch of the impeller which most of the twin scrolls seem to do.

If you change the pitch of the impeller there is an exponential relationship in terms of power required to spin it. A small change and the stock engines can probably still reach the same RPM or maybe slightly more to pick up top end, too aggressive with the pitch and you won't have enough power to spin it fast enough and lose top end.

If you notice on the twin screw impellers the 1st part of the scroll is smaller just like the inducer setup.

Berkeley Jet Drive - Inducer Pre-Impeller Cavitation Reducer

Inducer Pre-Impeller Cavitation Reducer

www.berkeleyjet.com

I am not entirely positive why they aren't installed from the factory but I would guess cost?

There is a lot research into jet pumps and sizing of intake, suction, runner lengths, impeller placement, etc to create the ideal pressure zones way above my understanding.

https://www.sciencedirect.com/science/article/pii/S209267822100056X

 

[FSH 210 Sport]

Similar concept to "inducers" run in the axial style pumps. The 1st scroll of the impeller helps to load the pump faster because it shortens the distance from the intake to the impeller. The first part of the twin screw/inducer also starts to rotate water for trailing edge of the impeller to make the pump more efficient. They also help the boat stay loaded in turbulent conditions, a lot of river race jet boats run them. Theoretically you won't pick up any top end speed unless you change the pitch of the impeller which most of the twin scrolls seem to do.

If you change the pitch of the impeller there is an exponential relationship in terms of power required to spin it. A small change and the stock engines can probably still reach the same RPM or maybe slightly more to pick up top end, too aggressive with the pitch and you won't have enough power to spin it fast enough and lose top end.

If you notice on the twin screw impellers the 1st part of the scroll is smaller just like the inducer setup.

Berkeley Jet Drive - Inducer Pre-Impeller Cavitation Reducer

Inducer Pre-Impeller Cavitation Reducer

www.berkeleyjet.com

I am not entirely positive why they aren't installed from the factory but I would guess cost?

There is a lot research into jet pumps and sizing of intake, suction, runner lengths, impeller placement, etc to create the ideal pressure zones way above my understanding.

https://www.sciencedirect.com/science/article/pii/S209267822100056X

In terms of power required to spin the jet pump, I once saw and cannot find at this time, a power requirement curve for Berkeley jet pumps, at 5000 rpm the pump required 350 hp, at 6000 rpm the demand was 725 hp. There is an exponential increase in power demand as the pump reaches its peak rpm.

 

[jetboatcool]

In terms of power required to spin the jet pump, I once saw and cannot find at this time, a power requirement curve for Berkeley jet pumps, at 5000 rpm the pump required 350 hp, at 6000 rpm the demand was 725 hp. There is an exponential increase in power demand as the pump reaches its peak rpm.

See attached. Depends on different cuts with "AA" being the most aggressive.

 

[FSH 210 Sport]

See attached. Depends on different cuts with "AA" being the most aggressive.

Dude! That’s awesome! Thank you!