How To - Choosing an Impeller
Topic: How do you choose the right impeller?
Expertise Required: Jedi Master
- Do you have a 50hp bike or a 60hp bike?
- How much do you weigh?
- Do you have a scoop?
- Do you have a speed plug?
- Do you have any other mods (exhaust spacer, engine mods, etc)
- Do you have a new wear ring?
- Is your nozzle bushing in good shape?
With the above considered, then here's what I recommend (and note that others have their opinions that differ from mine)
- Aluminum - stock STRAIGHT BLADE
- Aluminum - stock CLIPPED EAR
- Aluminum - used on Seaflash/Jetstars (never seen one but heard of them)
- Stainless - SKAT TRAK 11/13 (used for stock bikes)
- Stainless - SKAT TRAK 12/15 (big motor, lots of power required)
- Stainless - 4 blade used on Seaflash/Jetstars
- Stainless - 5 blade used on Seaflash/Jetstart
- Bronze - Straight 13 degree
- Wear ring - make sure it's a good one with no grooving or nicks
- Impeller nicks should be ground down and smoothed out
- Sharpen the leading edges of the impeller blades a little. Don't go crazy
- Make sure the nozzle bushing is in good shape.
- Adding a super-scoop is a good addition as long as you DON'T put in a speed plug too.
- Adding a speed plug works good too - but modify the scoop like this
- The skat trak will lose a mph or two on the top end, but has much better holeshot and midrange over stock. Many wetbikers agree that it's a good tradeoff.
- Scoops - the Super Scoop works BEST without a speed plug, or works GOOD with a speed plug if modified, and the Ultra Scoop works best with a speed plug. The Pro Scoop works best with a speed plug.
Which scoop is which? . . . look here
If you have a speed plug (aluminum or fiberglass) then your choices should boil down to the following:
- Aluminum clipped-ear - really good top end, good overall performance
- Stainless Skat Trak 11/13 - excellent holeshot, and midrange
- Bronze 13 degree straight pitch - little slower holeshot, but best top end
- The trend here seems to favor the BRONZE 13 degree prop. Watercross of Texas even used to re-pitch these but I don't know what they final pitch was.
- Since those bronze ones are hard to find, the Skat Trak 12/15 is another good choice.
- Running either of the above requires the nozzle bushing and shaft to be in good condition. Any wear/play there will quickly destroy the wear ring.
- Both of the above will probably require adding shims so that the leading edges of the impellers don't contact the pump casting.