Increasing Magnum pump setup

[CARBONX2]

If a 320lb ski spins a 13/18 in a 144 Mag with 84mm exit, what would be the next size to try? I have a 146mm, should I put a 13/18 in it? Exit nozzle size?
I have had a 16/21 in and it pulled harder but had a slight delay due to the tall pitch

 

[vitalikol]

Call Impros

 

[Matt_E]

If you haven't already done so, it might be worth your time to check the pitch of both impellers to make sure that you really have a 13/18 and a 16/21.

 

[Big Kahuna]

sounds like you need a 14/19 or 20

contact Dave at IMPROS and get a Hooker.

 

[CARBONX2]

I have contacted Dave, chatting on options. Tweaked carbs today, gave me more spin and less drive

 

[McDog]

I'm interested in the 13/18 if you get rid of it.

 

[Big Kahuna]

How is tweaking carbs going to change your pump setup?

Yeah, you may muddy it up some to where the motor is lagging causing you not to use the power you got. But that is more detuning than tuning.

 

[CARBONX2]

More hp causing prop to spin more and bite less

 

[Big Kahuna]

You need to pitch up then.

 

[CARBONX2]

I think now that the carbs are right that the 16/21 will work. With all the talk of bigger pumps with lower pitches, I am wondering what the equivalent of a 144mm-16/21 would be in a 146mm, how many numbers the pitch would drop

 

[CARBONX2]

Skat advised to try 16/18

 

[CARBONX2]

Tried 16/18, spinning basically gone, but 16/21 has much more arm-wrenching drive so fitting it back.

 

[McDog]

You should sell me that 144mm and move up to a 146! I might want the 146mm if you want to sell it instead.

 

[RiverRat]

15/19 in a 144 mag...... sounds like you are making some good power

 

[upstand2]

I'd say the bigger pump is the fix. I had a similar problem with mine. I got a hold of an old 19-21 mod impeller with a 4mm bigger hub. It helped a bit.

 

[CARBONX2]

15/19 in a 144 mag...... sounds like you are making some good power

Pretty good for stock bore and stroke SXR motor, the rest of the package is off the wall though

 

[CARBONX2]

came down from 84mm to 83mm on exit and changed from stubby cone to medium cone. Ski now gives whiplash:smokin:

 

[MNTURBO]

contact Dave at IMPROS and get a Hooker.

i didn't think hookers were recommended for mag pumps?

 

[sjetrider]

If a 320lb ski spins a 13/18 in a 144 Mag with 84mm exit, what would be the next size to try? I have a 146mm, should I put a 13/18 in it? Exit nozzle size?
I have had a 16/21 in and it pulled harder but had a slight delay due to the tall pitch

this is a 146 pump? Just pitch the 13/18 to 14/19. If you send it to Youngs Performance he will do it for you for $30 I think and turn it in one day. Otherwise find someone local that can pitch it (bass Boat shops sometimes do it). Or send it to Impros and wait.
If it is a 144 pump I have a 15/18 you can try and send back if you want.

 

[rollin5150]

Need to get one of these

http://www.watcon.com/Catalog_Pages/Impeller_Pitch.htm

Pitch it yourself for fine tuning.