Who has experience with twin screw impellers?

[FSH 210 Sport]

Ok so used that calculator you posted for altitude and it looks like currently the lake I go to with all the current weather inputs shows a altitude of almost 7600 ft elevation. Conditions are almost identical to what they were Saturday. So with that being said should I have Glen repitch it again for around 7500ft ?

Did you have Glen pitch them for 4200’ as mentioned in an earlier post?

You need to contact Glen and tell him what rpm’s you are getting now and he will adjust. I would tell him that the density altitude is 7600’ of elevation and see what he says. In my experience he was very willing to help me out and worked with me to get the best out of my set up.

It also depends on whether or not this will be where you use the boat exclusively. It that is true then go for the 7500’ of elevation.

If it was me, and the fact I go to lower elevations, down to 1500, I think I would split the difference.. to maybe around 6000-6500‘ and see what that gets you.

I meant to put this in my last post. I spoke of the cavitation thing. With my OEM impellers I could punch off from idle with no cavitation and it would leave hard, but would then pretty quickly start to flatten out acceleration wise. With the impellers I have now, if just punch off from idle both pumps will cavitate then recover. However, if I walk the throttles up pretty quickly there is no cavitation, but the boat does not launch / leave as hard as it did with the OEM impellers, BUT BUT BUT, as the boat accelerates there is what I would call a mid range hook where you can feel the boat really start accelerating hard where it would be falling on its face with the OEM impellers. It’s like having 3:33 end gears in a truck, in first gear it will pull very hard, but as you put more load on the truck the performance starts dropping off and the engine will not rev up into the power band so to speak. Then you 3:55 or 3:73 end gears in it, if you punch off in first gear you will spin the tires at first, but once it gets going and it hooks up it will start to accelerate hard where with the 3:33 end gears it was falling on its face.

Everything is a trade off. But right now, you need to trade off pitch to get your engine up to rated rpms where the engine is making peak hp and is flowing the most air.

 

[Dirtymunoz]

The engine has 78 hours on it so far. I bought it with 76. I will do a compression test today to see where I'm at and post results. I'll call Glen in a bit and see what he says

 

[FSH 210 Sport]

Thank you , That right there gives me hope honestly. Exact same scenarios for me and this boat and if you were able to get them resolved than it gives me hope that it is just the repitch that is needed. I was hoping the 4500 pitch on the new dual would be enough but never thought about actual altitude with the other factors in play. Let me know how your boat does with big Mable. I've been wanting to get a 3 seat tube but with just this 2 seater and boat issues I didn't wana spend money anymore lol

Jet pumps are kinda weird … there was a hp / rpm graph I saw for a Berkeley jet a while ago, to turn the pump at 5000 rpm it took 350 hp, to turn the pump at 6000 rpm it took 730hp. Unlike a propeller in open water, there is no where for the water to spill off of the blades since the impeller is ducted. As the pump increases in pressure / volume it becomes more efficient, so there is an exponential increase in demand hp. So its the big double whammy… the demand hp is going up, but your engine cannot spin fast enough to flow enough air to make rated hp, so you are caught at that point on the graph where demand hp is intersecting with available hp and then you’re stuck. That’s where I was at too. But now my engines can make the most power possible at my density altitude due to the fact they are spinning very close to rated rpm, the hp loss is still there, but now the hp loss is at the rated rpm / peak hp rpm, and not at the lesser hp of 6500-6900 rpm, again, the double whammy.

 

[FSH 210 Sport]

The engine has 78 hours on it so far. I bought it with 76. I will do a compression test today to see where I'm at and post results. I'll call Glen in a bit and see what he says

Damn! That thing is practically brand new! I’ll be very surprised if there is an issue with the compression.

When I tested my boat on the Mississippi river at 750’ of elevation it shot right up to 44mph on the speedo. As soon as I got up to my area, with 5 adults on board it would only do 29mph.. 29. I didn’t buy a speed boat, but dang that was a lot of mph loss. Remember, perfection is a direction not a place. You will find the right compromise that will have you and your family all smiles and loving your time on the water! And with that single normally aspirated 1.8L you be having a lot of smiles per gallon!

 

[Dirtymunoz]

Damn! That thing is practically brand new! I’ll be very surprised if there is an issue with the compression.

When I tested my boat on the Mississippi river at 750’ of elevation it shot right up to 44mph on the speedo. As soon as I got up to my area, with 5 adults on board it would only do 29mph.. 29. I didn’t buy a speed boat, but dang that was a lot of mph loss. Remember, perfection is a direction not a place. You will find the right compromise that will have you and your family all smiles and loving your time on the water! And with that single normally aspirated 1.8L you be having a lot of smiles per gallon!

What was the elevation change ?

 

[FSH 210 Sport]

What was the elevation change ?

The elevation change was 4,250’.

I test drove it at 750’ above MSL on a cool damp/rainy morning…it was probably in the mid 50’s. Perhaps 903’ density altitude, relative density 97.38%, or 2.62% hp loss. 222 hp-2.62%=5.81 hp @rated rpm. 44 mph @ 7800-8000 rpm, with two people, 20% fuel, trolling motor and batteries no other gear.

When I got home and took it on its maiden voyage I was at 5000’ above MSL on a clear warm day, probably about 80°. Density altitude of 7700’, relative density of 79.36%, or a 20.64% loss of hp @rated rpm. 222-20.64%=45.82hp 29 mph @6500 rpm, with 5 people, 50% fuel, trolling motor and batteries no other gear.

The most recent test I ran was on a clear cool morning 60° at 5000’ above MSL at 6465’ density altitude 6465’ relative density 82.41%, 222-17.59%=39hp loss @rated rpm. 41mph @7850rpm, 1 person, 100% fuel, trolling motor and batteries, and at least 500# of load over those original performance numbers.

Sorry I don’t have an apples to apples comparison and Yamaha is not forth coming with hp / torque charts. The only hp numbers available for the TR-1 engines is the label on the motor which shows 83Kw, 83,000 / 746=111.26hp

 

[Dirtymunoz]

Welp, got the twin impeller repitched to 7800 and went to test it today and with just myself on the boat she did about 30-31 at 7000-7100rpms. turns were a bit better but still bled off about 8-10mph on hard turns and about 5 on smooth turns. Came back and picked up 3 small kids and 2 more adults and was able to get around 20mph at 7000 rpms. It did plane out around 8 seconds so it did better than before but once at 20ish and trying to turn she started becoming an anchor again. It didn't come off plane like it did before buy it was enough to not be able to swing the kids on the tube very much. Had a very hard time trying to swing them out of the mid spray. With today's conditions density altitude was around 6500 ft . Just truly disappointed on this boats performance, I know its not a pure tow sports boat but looks like I'm just gona sell it at this point. I was hoping this pitch and dual was gona fix issues but just bummed out already

 

[Dirtymunoz]

Update on this. Ended up selling the boat to someone in Colorado. He was having same issues up there and ended up having the factory impeller pitched by some one in the state and let me know it runs like a champ now supposedly. I did let him know of the issue before he took delivery and I'm glad he was able to get the proper pitch figured out.

 

[Cambo]

Installed the twin impeller set up with lucky 13 cones and SS wear rings. I have had the opposite of what @Dirtymunoz experienced The boat jumps onto plane in less than 2 seconds and for surfing it pulls upto wakesurf speed much better with out having to hit max RPM and zero cavitation. The wave produced is better its cleaner this is most likely due to the nozzle directing the flow in a more precise stream kind of like when you adjust the spray on a hose nozzle it goes from fan to a perfect stream

 

[FSH 210 Sport]

Installed the twin impeller set up with lucky 13 cones and SS wear rings. I have had the opposite of what @Dirtymunoz experienced The boat jumps onto plane in less than 2 seconds and for surfing it pulls upto wakesurf speed much better with out having to hit max RPM and zero cavitation. The wave produced is better its cleaner this is most likely due to the nozzle directing the flow in a more precise stream kind of like when you adjust the spray on a hose nozzle it goes from fan to a perfect stream


View attachment 206556View attachment 206557View attachment 206558


View attachment 206559

Glad to see it was a success !

Where did you get the impellers?
Looks like you are at sea level?
What are your WOT rpm’s?
Did you notice a reduction in top speed? It was my understanding that the twin impellers are great for wakes and towing but sacrifice some top speed?

 

[Cambo]

Where did you get the impellers? Another member but I think it was impros that was the original supplier
Looks like you are at sea level? Normally at sea level that was Lake Bomoseen VT 410" ASL
What are your WOT rpm’s? Need to double check but I think it was 7600
Did you notice a reduction in top speed? Im not a top speed guy if I was I would make the boat lighter by removing the extra 300lbs of items stored in the boat but i think its down by 1-2 mph It was my understanding that the twin impellers are great for wakes and towing but sacrifice some top speed? Its minimal

 

[FSH 210 Sport]

Where did you get the impellers? Another member but I think it was impros that was the original supplier
Looks like you are at sea level? Normally at sea level that was Lake Bomoseen VT 410" ASL
What are your WOT rpm’s? Need to double check but I think it was 7600
Did you notice a reduction in top speed? Im not a top speed guy if I was I would make the boat lighter by removing the extra 300lbs of items stored in the boat but i think its down by 1-2 mph It was my understanding that the twin impellers are great for wakes and towing but sacrifice some top speed? Its minimal

Thank you for answering my questions!

Impros brought up the twin impellers when I was doing my high altitude project on my impellers and they are the ones that told me about the increased hole shot / towing and mid range performance at the expense of a little top speed. I’m not really a top speed guy, well too much, I do like to zip around at the end of the day.

Again, glad you had success with these and it improved your boating experience!!!!

 

[Wicked92]

My leadingedgeimpellers.com (original owner of impros) twins are due in today via ups. Doing them this weekend. David Stewart the owner has been nothing but awesome thru the process. Mine are custom pitched, not just outta box pwc solas pieces.

 

[jacoviii]

David told me to wait to see your results. Where are you located for elevation purposes.

 

[Wicked92]

David told me to wait to see your results. Where are you located for elevation purposes.

Nj..... at sea-level

 

[anmut]

My leadingedgeimpellers.com (original owner of impros) twins are due in today via ups. Doing them this weekend. David Stewart the owner has been nothing but awesome thru the process. Mine are custom pitched, not just outta box pwc solas pieces.

Eagerly awaiting results!

 

[FSH 210 Sport]

My leadingedgeimpellers.com (original owner of impros) twins are due in today via ups. Doing them this weekend. David Stewart the owner has been nothing but awesome thru the process. Mine are custom pitched, not just outta box pwc solas pieces.

well? Anything to report?

 

[Cambo]

Another thing that I noticed the pissers look like they have a higher flow. This would most likely be due to the lucky 13cones loading the jet nozzle with more pressure. Higher flow better cooling the new motors are set up for more cooling the aluminum heads need to keep cool so this should be helpful

 

[anmut]

I emailed Leading Edge on these - $1700 for a pair! DAMN. Out of my range for this season...

 

[Wicked92]

well? Anything to report?

nothing yet, working on it tomorrow. Got too jammed up to chance taking it apart and not have back together for weekend. Hopefully this weekend testing.