Other Let's talk about props

[Midlake Crisis]

Before I got in to Jetskis I was in to old school jet boats.
In that community there is a great deal of attention given to matching props (impellers) to torque and HP curves to reach specific performance goals.
Around here it seems that there are some impellers that seem favored over others, but it is all very general and vague, without much discussion of theory.
Thoughts?

 

[Boris]

Without a large assortment of props to try back to back, most just settle for what is suggested to them and live with it.
I used to take a pitch gauge with me to the beach and tweak the prop with a cresent wrench but that was on a couch and all I cared about was top speed. Now I couldn't be bothered.


Sent from my iDiot device

 

[kevbo]

Before I got in to Jetskis I was in to old school jet boats.
In that community there is a great deal of attention given to matching props (impellers) to torque and HP curves to reach specific performance goals.
Around here it seems that there are some impellers that seem favored over others, but it is all very general and vague, without much discussion of theory.
Thoughts?

Yep, pumps are just another meaningless name and number to the average jetskier, just like carburetors. Popularity is all that counts, this is a world where perception is reality. Its mainly because most participants are young and/or only interested in riding. Most tech guys are old.

 

[FlightPlanDan]

Before I got in to Jetskis I was in to old school jet boats.
In that community there is a great deal of attention given to matching props (impellers) to torque and HP curves to reach specific performance goals.
Around here it seems that there are some impellers that seem favored over others, but it is all very general and vague, without much discussion of theory.
Thoughts?

You're right. But I don't think it's because nobody cares to do the research.
I think it's because the mods ski to ski vary so much that a table or curve would not be accurate. Not all can dyno torque and HP.

It seems to be less expensive to simply try a few different props and dial in on what works for your ski.
I'd love to see some software that you could plugin your mods, compression, etc... and be told what prop would be best for your application. But....for now trial and error seems to be the SOP.

 

[sportfish258]

I think the diffrence is methods of measurement. Race guys can use a stop watch /distance there you can see a clear improvment. With freestyle / freeride it is feel. I think the best way to set up your pump is to work closely with a builder or learn to make small adjustments on your own and have a builder do the fine smoothing WITH YOUR PROP GUAGE. It would be a lot of work and expensive either way. That's why most run a prop and end up just settling.

 

[Aircraftsalz]

There's a lot to be said about props. But most people just install and ride... I know with my ski I've had the pump in and out more times than I care to say. It's not just the pitch of a prop. It's how you load the prop, washer or no washer, intake grate, reduction bore size, steering nozzle bore size, then you have to match the carb tuning to that prop in some cases. All those fine tweaks can really bring the performance out of a prop.

But the finally deal comes down to how the prop feels to the rider.

 

[sportfish258]

There's a lot to be said about props. But most people just install and ride... I know with my ski I've had the pump in and out more times than I care to say. It's not just the pitch of a prop. It's how you load the prop, washer or no washer, intake grate, reduction bore size, steering nozzle bore size, then you have to match the carb tuning to that prop in some cases. All those fine tweaks can really bring the performance out of a prop.

But the finally deal comes down to how the prop feels to the rider.

Well said . You can spend a month of sundays tuning and still wonder if there is a little something you could do to get more. LOTS of different combos that add up .

 

[OCD Solutions]

Or you could drop in one that works and just rip it. There are so many variables in surf from one ride to the next that small differences in the prop don't concern me. You guys looking for that extra 25 RPM have way more time to play than I do. I can understand it for the racing and freestyle guys but those of us who freeride, the difference is negligible, (or rather, just not worth the bother).

 

[McDog]

I find people who have similar setups and ask. Then I ask the pros. Then I ask some more and compare it all and obsess over it until I finally decide.

Props to Aircraftsalz and Jetmaniac for helping me decide to run a 14/19 in my 144 mag pump with my ADA motor in a lightweight hull. I went against the advice of some other pros to listen to them but I was glad I did. It was spot on. Finding someone you trust who has been there and done that with a similar setup is priceless.

One more great benefit of X-H2O! Thanks guys!

 

[harrypotter]

Or you could drop in one that works and just rip it. There are so many variables in surf from one ride to the next that small differences in the prop don't concern me. You guys looking for that extra 25 RPM have way more time to play than I do. I can understand it for the racing and freestyle guys but those of us who freeride, the difference is negligible, (or rather, just not worth the bother).

how very un ocd of you lol

 

[Idok]

how very un ocd of you lol

ha..good one..I thought the same thing

 

[Waternut]

I think the diffrence is methods of measurement. Race guys can use a stop watch /distance there you can see a clear improvment. With freestyle / freeride it is feel.

Exactly... The majority of your boat engines will be a fairly stock or commonly modified car engine. This makes determining torque and hp very easy. You could swap ported big bores all day long in the exact same ski and inevitably, they'll all be different. You also have a speedometer that you can clock your acceleration times with in a boat. Even if you had a speedometer on your ski and could time it, you would come up with massively different numbers over 10 runs purely because you can't just nail it. You have to ease into the throttle to prevent the nose from coming out of the water which will make all your numbers moot.

The only real way I can think of to get hard numbers is to have a G meter mounted to your tray. I think it'd be cheaper than buying new props, nozzles, etc all day but requires some electrical know how, lots of waterproofing, and the system would need a downloadable log for review. At least then you could tell if you're increasing your acceleration and if it's smooth acceleration. Even then, that's a lot of work and money to dial in a change that may or may not actually get you an improvement.

 

[OCD Solutions]

how very un ocd of you lol

ha..good one..I thought the same thing

My OCD played into the selection stage which is the way it should be done rather than mix and match later. I harassed X-Scream, Impros, Skat and countless people here on the X for 6 months on prop selection. Once I made my selection and felt how good it was, I didn't see the need to play any further. I also had Dave at Impros assemble the pump and shim it as tight as possible to give me every bit out of it as he could.

I was told to go with a 13/18 as well but after talking to Josh, Lucas and Chris and heard the performance they were having with the 14/19 in the 144 Setback pumps, I felt it was a sure thing and I have not been disappointed.

If you need a device to tell you there's a difference...there's not enough difference to really matter, to 95% of us anyways, (there's always the few that get hung up on numbers).

 

[harrypotter]

i will be running 14/19 c75 with tbm on my xscream 865 as recommended by xscream i may tweak slightly if i think i can get a little more out of it but gotta go with what the engine builder says to begin with . was thinking of getting a mag but my turbo diesel car just blew the turbo up ! $1900 so thats mag out the window for now

 

[kevbo]

Pump load should be high on the list of priorities. Missing the power bubble will undo a lot of $$$$$ worth of engine mods. Big engine guys have it easy because they can pull anything in a 144 pump. Small engine guys need to put in the time if they want a really good running boat.

 

[OCD Solutions]

Some setups are more finicky than others too. I had troubles dialing in a seadoo motor years ago and the key was the prop. I built up a ported 951 with a coffman pipe and rossier head, novi carbs and a ton of little things and messed with jetting for 2 seasons after. Bill Oneil finally clued me in that the coffman pipe made very little bottom end and needed a very special pitch to get it out of the hole and on the pipe. The powerband was so narrow it was stupid and keeping it in tune was a nightmare.

All my standups were much easier to deal with and it seems you could run just about any pitch with decent results. I think the weight of the craft plays a big role in impeller pitch. Typically our standups have much better power to weight ratios than couches so it gives us some forgiveness on pitch selection.

 

[Octane_114]

There's a lot to be said about props. But most people just install and ride... I know with my ski I've had the pump in and out more times than I care to say. It's not just the pitch of a prop. It's how you load the prop, washer or no washer, intake grate, reduction bore size, steering nozzle bore size, then you have to match the carb tuning to that prop in some cases. All those fine tweaks can really bring the performance out of a prop.

But the finally deal comes down to how the prop feels to the rider.

very well said, this is very true, i cant tell you how many times i have had my pump off my x2, going with diffented intake grates, tri scoop, or worx is best for me, and asking everyone their set-up, i talked with impros and started with a c75 13/17 then 14/19, then talked with jon (jonnyx2) and the c75 set at 10/18 fit my set-up best, rpms stayed in the range i wanted 6800-7023. he helped me out super cool dude explaned some theory, well just about the rake and pitch angle. lots of different comhos that bring
it all together, whats right for me others my not like.

 

[Octane_114]

impellers are a maror part part of the set-up, you can have all the power in the world but if you cant hook it up and keep it hooked up what good is it? i do all flat water riding, to me being able to hook up on the bottom and pull to the top and being able to stick it in a turn stay hooked up "like riding a rail" pulling out of the turn like your on a rocket! intake pump stuffer having the pump set back and the correct impeller selected. working the pump shoot/intake track to keep the pump loaded helps too, well i guess i'm leaning more to the x2 i have ever rolled over a sj. i have riden a stock sj and was impressed with the power it had in stock form.