Can someone please explain the benefits of a bigger pump to me?

[dbrutherford]

I was looking on Waterdawg's site where he makes a pump shoe to fit the 155 Yamaha pump into an SJ which normally has a 144 right? I know a Kawasaki 650/750/800uses a 140.

So what does the bigger pump give you? I am guessing more thrust since it has more volume. But I remember reading how Skat was making Mag pumps that were shimmed down to 144 or 140 for an SJ. Can someone fill me in?

 

[Foximus]

well... when you look at the purpose of the mag pump and TBM cone that kinda leads one to wonder....


However, I guess when you got a worked 1200 motor and every other goodie... you can push that extra volume and still keep a high velocity

 

[superramjet]

you can prop almost any size pump to work, however when you are running 23/28 props in a 140 you can get more thrust and effiecency with a lower pitched prop like a 15/20 in a bigger pump. The big pumps have a whole different feel to a small pump. bigger pumps hook up harder and glue the boat to the water. . I've run the 148mm and it pulled like a tractor, however it never wanted to leave the water like the smaller 144mm. I"m unable to run a 140mm in my setup because the prop i need is not readily available and its cost prohibitive to buy 3-4 custom made props to figure out what to run. I can run a 144 and select from non custom props. My opinion is the 144mm is the best size for freestyle freeride. And with a mag 144, different cones and boring nozzles you can prop just about any motor to work well with it.

As far as kawi's i know none of the big horse motors are running the 140, i see alot of 142 mags and 145 mags (malone)

 

[kevbo]

Our axial flow pumps are simply ducted fans running in water. Water does not like low pressure so maximum impeller tip speed and blade angle are limiting factors. They suffer excessive cavitation when the blade angle is too steep and/or rpm is too high. Common axial flow pumps have a fairly wide operational range so its easy to make most combinations work well. You will notice that smaller high rpm engines do best with smaller pumps and large displacement engines make better use of larger pumps.