Seadoo pump behind snowmobile engine

[Quinc]

For anyone who wanted to know what a snowmobile engine would be like in a pwc.

Top end is great but he has to get the boat out of the water so he can suck in some air and get the rpms up. After that it fly's. Trying to help out with some pump tuning (yes put a pwc engine in would be best idea, but what fun is that!) What do you all think; shim the impeller away from the pump and bore the nozzle. I know nothing about seadoo pumps, is there a well known low pitch XP 140mm impeller that works well with them? Add water injection to the pipe?

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Pump is a 140mm

 

[Storbeck]

I think you can fit Kawasaki impellers in sea doo pumps and that would provide options with lower pitch than what's typical in a sea doo.

 

[WFO Speedracer]

I think you can fit Kawasaki impellers in sea doo pumps and that would provide options with lower pitch than what's typical in a sea doo.

You can't , at least without mods you can't , impeller backspacing and splines are different, Seadoo uses crown splined shafts, Kawasaki uses straight splined shafts..

What engine is that, how many HP is it rated at , how many RPMs is it turning or rev limited at , that would give me a general idea of where to start on an impeller recommendation, I have tons of stock Seadoo impellers here BTW Somewhere here I have a nice Solas , maybe a 12/25 or something along those lines.

STOCK IMPELLER CHART IS HERE : https://seadoosource.com/impellerref.html

Don't look at any of the RFI models although the pitch is in the ballpark those are all big hub impellers and won't work with that pump.

So looking at the specs that is somewhere between 120-140HP and turning 7800 -8000 RPM , that falls in closely with a 96-97 XP , 97 SPX , all 110 HP and have the 140mm pumps .

 

[Quinc]

You beat me by a minute with the specs!

Prop is a 16/23

 

[WFO Speedracer]

Yeah you need a much lower starting pitch and probably a couples of degrees on the ending pitch.

An HX-GTI impeller could work with some rebend on the rear blades .

 

[Quinc]

After taking out the prop to check pitch he found he needs to rebuild it:

 

[WFO Speedracer]

Yeah I would say so lol.

The Solas impeller I have is a 17-26 , it wouldn't do you any good , the main issue with snowmow engines is the porting , those are set up with a clutch system that gives them a running start usually 4000 + RPMS , you may not be able to overcome that without a custom impeller .

If it was a powervalve engine you would have more options such as installing stronger springs to keep the exhaust valves closed longer but from the pics you posted it doesn't look like it is.

Don't buy Seadoo jet pump oil it/s expensive as rip. Mobil one synthetic, Lucas synthetic or Royal purple synthetic are all good options available at any auto parts store , you are looking for 75 w 90 weight.

 

[WFO Speedracer]

I wonder what would happen if you ran the big hub RFI impeller in the small hub housing, my understanding is that's what the Hooker impellers are and I know they run them in X2 small hub pumps. I have never tried it on a Seadoo pump.

That RFI 140mm impeller is a 12/25 , it might be worth a shot. I am sure there are several here if you want to try one out.

 

[kevbo]

If he wants to get up to 7800-8000rpm, a very flat impeller will be required for a 700cc engine. I know old seadoo props are almost identical to Kawasaki 650s but were generally higher pitched. I have found new Solas 9-15 and 11-16 concords for Kawasaki 750s are the flattest props available and can be easily cut for 650 or seadoo use.

 

[WFO Speedracer]

If he wants to get up to 7800-8000rpm, a very flat impeller will be required for a 700cc engine. I know old seadoo props are almost identical to Kawasaki 650s but were generally higher pitched. I have found new Solas 9-15 and 11-16 concords for Kawasaki 750s are the flattest props available and can be easily cut for 650 or seadoo use.

Like I keep saying but no one is listening, those Kawi impellers will not just slide onto a Seadoo driveshaft, yes I fully realize they use the same impeller tool , but the splines are slightly different since Seadoos are crown splined and Kawis have straight splines , you also need to realize I am the guy that would know this for sure.

Back in the day when we were hopping up the old 580 Seadoos we ran 16.5 straight pitch impellers and bumped the rev limit, those engines only turned 5550 RPMs from Seadoo , we bumped them on up to 7000 - 7500 and they ran like a raped ape , it is possible you could do something like that here as well but starting with maybe a 18 or 19 pitch, who knows , you are probably going to have to be the test subject on this one.

I am offering to send you some impellers I think might work , if one of them works pay me a reasonable price for it if not it will only cost you shipping back to me , either way right now you are shooting in the dark , at the least this would give you an idea where to point..

 

[kevbo]

Then he needs to adapt a Kawasaki shaft since ALL seadoo props are too tall. Ive used old 14-17 seadoo Scats in Kawasaki 650s and never could tell any difference.

 

[Storbeck]

I don't think it will be enough to get him where he wants to be, but as a quick and dirty improvement bore the nozzle as much as possible. There were different sized oem sea doo nozzles weren't there? At least make sure it's the biggest of the oem options.

I'm not arguing about the difference in splines, if you're saying they're different I believe you, but if the impeller will slip onto the shaft, what's the harm? Seems like kawi splines are pretty sloppy fit on the shafts already.

I was assuming that somebody with the ability to build that boat could arrange to machine the impeller for whatever back spacing adjustments are needed. (and probably can bore a nozzle).

 

[WFO Speedracer]

Then he needs to adapt a Kawasaki shaft since ALL seadoo props are too tall. Ive

used old 14-17 seadoo Scats in Kawasaki 650s and never could tell any difference.

kevbo with all due respect stick to what you know.

Seadoo impellers will fit on Kawi shaft , sloppily but yes they will fit, the reverse is not usually true , yes it is possible you might find an old impeller with sloppy worn splines that will fit on a Kawi shaft but it's not that likely.

99 GSX RFI has a 140mm pump with a 12/25 impeller, that would probably be a good start ,

 

[WFO Speedracer]

First pic Seadoo driveshaft splines notice the crown on the spline, it's bigger in the middle than on the ends .that pic is of a Spark driveshaft but they are all made the same.

Second pic Kawi impeller tool, straight splines just like on their driveshafts, so of course that impeller tool or driveshaft for that matter will fit in a Seadoo impeller but since the Seadoo splines are slightly bigger in the middle it's just far enough off that it won't usually go on.

Trust me I tried it on my X2 with the 787 engine, Kawi driveshaft and Seadoo pump.

 

[kevbo]

My experience with a Seadoo mix is using a "low" pitched seadoo 580 prop in a kawasaki 650, it worked perfectly. I also know that it will take a really big snow engine to pull the typical seadoo prop up to 8000 rpm. His options will open greatly if he learns to bend blades or just use kawasaki props.

 

[WFO Speedracer]

My experience with a Seadoo mix is using a "low" pitched seadoo 580 prop in a kawasaki 650, it worked perfectly. I also know that it will take a really big snow engine to pull the typical seadoo prop up to 8000 rpm. His options will open greatly if he learns to bend blades or just use kawasaki props.

How do you figure , there are way more Seadoo models that used 140mm pumps, everything from a SP with a 580 and 60HP to a 1997XP with a 787 and 110hp , big hub and small hub to boot, I posted the impeller chart lots of options there . Seadoo impellers start at straight pitch 16.5 to progressive 12/25 and all the impeller backspacing are the same.

Bottom line here is this, its a porting and pipe issue , it may or most probably may not be easily fixed by an off the shelf impeller swap , regardless of the brand ..

 

[TheBuzzard]

Seadoo splines and kawi splines are very close. I use a seadoo shaft to remove all my kawi props. Shaft is a hair looser in the prop snout and on the back side seadoo has a funky lip where kawi is just flat to fit against the spacer that the seal rides on. I'm sure a kawi prop could easily be modded to work. Not sure whether 750 or 650 since the back depth is different. Pretty sure drunk Doug porter brought a superjet to the river 20 years ago with that same powervalve Polaris motor in it. He worked at adrenalin powers ports and also for Mike koe as a wrench.

 

[G-Body]

How about if you give the pump some air until that thing gets up on the pipe? 1" or a couple 3/4" NPT bungs in the intake side of the pump with an electronic solenoid valve. Let it pull some air into the pump until it spins up then use a window switch to close the vents.

 

[WFO Speedracer]

The dude has enough to sort out already without going to the hassle of converting differently backspaced impellers with questionable fitting splines , but hey I have never done any kind of crazy conversion skis myself , so you should probably listen to these guys who had a friends uncles cousin with a totally different set up in their ski, that would be my best advice.

So that's a dry snowmow dry pipe I assume , but what if you injected water into it anyway , I have seen some guys do this on Superjet dry pipes to slow the wave down some making it come on the pipe quicker , it's a steel pipe so easy enough to weld a bung on it , for testing purposes you could probably just drill and tap the pipe , install a fitting and tap it for Mikuni jets , just throwing some ideas at you.

 

[Myself]

My guess is that pipe/porting/carbs/etc.......appear to be set up for efficiency at around a 1.7:1 gear ratio in a sled. In a watercraft they are direct drive 1:1 to the impeller. This is probably leading to a bogging/soft low end that might be REALLY tough to try and "tune" in. I feel like a better course of action would be a simple gearbox with heavy duty gears (probably could be borrowed from a car manual transmission) and a slight change in the motor mounting position to accomodate the gearbox. You know, Yamaha did this exact thing when they modified an R1 bike engine for use in the Waverunner...........the gear reduction is in the rear housing of the engine, thus taking advantage of the designed powerband of the engine.