12/15 to low pitch....

[storey]

i have a 1990 superjet 650 with 12/15 solas concord, msd, stubby pump cone, intake grate. the impeller works great now but i just bought a 61x motor with 180 psi head and b pipe to swap in sometime next week. i am setting the ski up for all bottom end power.

is 12/15 to going to be to low of a pitch for the new setup?

if needed, what would be a good pitch to have the impeller repitched to?

thanks,

aaron

 

[Mouthfulloflake]

IO did the same thing.

650- with pipe, head, and msd.

12/15 cutback concord. WW cone. nozzle bored to 85mm

changed in a 701.

still awesome, and the bottom and top end got better.
it hit harder, and reved higher.

the 12/15 is LOW.

you might have to loose the cone, or stick with stock nozzle.

a 13/16 might give you good bottom and MORE mid-top though.

ive got one, I havent ran it yet.

the pitch of the impeller is always a comprimise, its all in what trade offs and gains you can live with.

 

[MADMAT]

Yea I doubt you will be able to do both cone and 85mm. So far it seems to be best with the 85mm over the stubby.

 

[douglee25]

too

 

[DaUpJetSkier]

so as far as moving up from a low pitch to higher as far as freestyle goes does it go 12-15, 13-16, 13-17? Makes sense to me but just making sure because I gotta pick ne of those soon for a ported 701, dry pipe, etc. I want all low end like everyone else. oh I got a WW cone and stock nozzle as of now.

 

[storey]

my exit nozzle is stock so i will just leave the impeller alone for now. pobably have impros repitched it to 13/16 and 3mm cutback sometime this winter.

thanks guys,


aaron

 

[romack991]

i run a 13/15 cutback in a ported 61x, bpipe, that has the ww cone and bored nozzle. i like it. just experiment by swapping the cones out back to back.

 

[SUPERTUNE]

Arron/Storey, If you have a little cavitation with the 12-15, Try and switch to a 701 81mm aluminum nozzle (81mm is stock on a 701 superjet) and a 650 is plastic nozzle I believe is a 84 or 85mm (forgot!).

 

[romack991]

my plastic nozzle was out of round. measured between 82 and 86mm.

 

[storey]

Arron/Storey, If you have a little cavitation with the 12-15, Try and switch to a 701 81mm aluminum nozzle (81mm is stock on a 701 superjet) and a 650 is plastic nozzle I believe is a 84 or 85mm (forgot!).

i will have to measure mine. good thing you posted that. i would have never guessed yamaha would put different exit nozzles on the 650 and 701 models.

so if someone with a 701 ski wanted a bored nozzle i could just swap them my stock nozzle for their stock nozzle?

aaron

 

[romack991]

doubt anyone would want to swap, the plastic nozzles (90-93) have a huge stock siphon bilge obstruction.

 

[storey]

doubt anyone would want to swap, the plastic nozzles (90-93) have a huge stock siphon bilge obstruction.

yeah kinda figured no one would want it. i'll start looking for a 94+ nozzle once i swap the engine.

 

[romack991]

i still use mine, bored it to 84.5mm and removed all that obstruction (slightly smaller than 85 to compensate for the 86mm sections) but that was a pain since you have to fill in holes.

you dont need to switch, he was just saying IF you do have problems with cavitation, you could swap out the nozzle since the newer ones are smaller and would provide a little more back pressure for the pump.

 

[meatball]

Huh, thats weird, my VXR PRO has the plastic exit nozzle, and my 91 650 SJ has the aluminum one. I keep finding weird bits like this that make it look like my ski used to be hopped up. IE b-pipe marks on the walls.

 

[SUPERTUNE]

If you want the best performance out of your superjet pump definitely upgrade to the late model superjet alum. nozzle, they do work a lot better (taperbored from yamaha)than the straight bored plastic nozzles. Then send to Pat @X-Metalworks if needing nozzle boring as I made him a fixture to bore them in a lathe to properly bore with an aggressive taper (not straight bored)

 

[keefer]

So they are tapered? Did not know that. I think I measured my 94 sj nozzle at 82mm at the very end. So how much are they tapered from the factory as opposed to after the mod?

 

[SUPERTUNE]

Now that I think about it more... your right! it is 82mm stock size, can't remember the exact degree angle... it's about +1 degree more than stock. (I have Pat's machinst Daniel machine them for me now so I have more time to port/build the motors)

 

[keefer]

Thanks, I am running an 83mm I got from a venture or something with the wammer cone and a Concord 13/17 non setback. Thinking of getting it cut back and repitched to 13/16 this winter. Works good now but could be better. Always something to spend more $ on :fingersx: