Super Jet suggested prop pitch

[keith t]

When i ran a 144mm pump in my superjet it had a 13/17 large hub swirl prop that was cut back 7mm

I am now running a 140mm mag pump - is there a direct read across to which prop is equivalent ?

 

[Big Kahuna]

Nope. Contact your builder or Dave at IMPROS

 

[keith t]

Mmmm. thanks for the reply - though i cant understand why there wouldnt be a readacross comparisson table

I understand why you have said contact the builder - but what would he be going off ? (as an aside i built it so i cant help myself here hence the post)

 

[Matt_E]

Who knows if your previous impeller was ideal for your engine?
Personally, I run a 13/17 in my 140 mag

 

[keith t]

13/17 was what blowsion advised when i sent them my engine & ski spec / and my weight etc

 

[Big Kahuna]

You cut stock 144 props (Skat, Solas) back to help with the pump loading. The Mag Pump is a much more effecient setup. You do not use the same props typically. Prop pitch is just like jetting. What may work on my ski may not work on yours.

Your builders or an impellor pitch specialist like Dave is the best way to go to figure out what is best for your setup.

 

[Matt_E]

Might be worth it to have any new skat impeller checked over. Numbers say one thing, but actual pitch seems to be something else very often

 

[keith t]

cheers BK and Matt, I understand what you are both saying, just thought there may be a rule of thumb EG 144mm pump using 13/17 is equivalent to 16/21 in a 140 etc etc

recognising that this will then be affected by cutback , engine, ignition curve etc etc

 

[Big Kahuna]

cheers BK and Matt, I understand what you are both saying, just thought there may be a rule of thumb EG 144mm pump using 13/17 is equivalent to 16/21 in a 140 etc etc

recognising that this will then be affected by cutback , engine, ignition curve etc etc

Add to that Reduction Nozzle size, stock cone or a wetwolf cone (Stock pumps), short cone, med cone long cone in a Mag Pump..........

Then motor size comes into play also. One setup may have enough power to allow you to run a bit taller prop than another............ just too many factors.