Impeller Upgrade Question

[VegasRatt]

If I put an impeller on my ski that is too progressive for the motor will it bring my RMS's down at full throttle? Kind of "bog" the motor down a bit?

[xlint89]

YES

You want to keep the engine's RPM where it's most efficient. Too steep an impeller will lug the engine and do harm.

[VegasRatt]

If I was to increase the size of the jet pump diameter by a millimeter or so that should alow more water to move through the pump and raise the RPM's up a bit right?

I only ask this because I installed a new impeller and don't have my stock one anymore so rather than buying a new one i want to see if I can get this one to work. I got the new impeller because I "was" going to build up my motor but that changed.

Thanks for the input.

[Bernie]

If you increased the nozzle inside diameter yes .If you increase the clearance too much between impeller and ring you will get cavitation

[K447]

If I was to increase the size of the jet pump diameter by a millimeter or so that should allow more water to move through the pump and raise the RPM's up a bit right?

Are you asking about increasing the diameter of the pump exit nozzle, or the diameter within the 148mm pump itself?

The exit nozzle you can increase in size, just don't over do it. There are special nozzles that have changeable rings, so you can easily change the exit diameter and see what size works best.

The jet pump body around the 148mm impeller, must match the impeller diameter. There is supposed to be only a tiny amount of clearance between the impeller and the wear ring surrounding it. Max clearance is 20 thousand, and that is considered way too much around here.

[32DegH2O]

The whole design of the pump was geared around the 148mm dia. dimension so I wouldn't mess with it. You can increase the dia. of the exit nozzel as others have mentioned but wouldn't go to much more than a 2-3mm. If it were me, I would sell the impeller and get the right one for your setup...don't think the exit nozzel will help get the rpm's up enough by just incresing the exit opening...not really the best way to go about it in my opinion.

[VegasRatt]

I got ahold of a stock impeller ( it is tore up a bit but works ) and now my RPM's are back up to where they need to be @ 6800'ish .... does anyone know what the pitch of the stock impeller is. I just looked up the one i purchased and it is a Solas PA-SC-X1 which i believe is a 14/21... i "think" the stock one is 17/21....

[K447]

I got ahold of a stock impeller ( it is tore up a bit but works ) and now my RPM's are back up to where they need to be @ 6800'ish .... does anyone know what the pitch of the stock impeller is... i "think" the stock one is 17/21....

What is the part number of your stock impeller?

[VegasRatt]

5132044

[K447]

5132044

5132044 = 7.0 mod, slim, overlay
1999 SLX, SLTX, Genesis