Super Jet Yam Magnum pumps, 140, 144 or 148mm "whats the diffrence"?? setback/non setback

Christian_83

Christian_83

Xscream
Location
Denmark
Hi all
Got some Q about the diffrent mag pumps.
What kind off power does the pumps require and what the limit for ex. 140mm and 144mm?
And why are the first magnum pump, smaller than the stock 144mm yamaha pump??
And how big diffrence is there between a setback and non setback pumps?
Regards from Denmark
 
Waternut

Waternut

Customizing addict
Location
Macon, GA
A setback pump will stay hooked up slightly longer in heavy chop because it has more volume of water in front of the prop but a lot of people don't think the extra benefit is worth the extra cost of a longer driveshaft. As for pump size, everyone has their own opinion and every engine builder also has their own opinion on what's best. However, you won't typically find a 148 pump in any ski except those guys who are running 1000+cc engines. Even then, Eric Malone runs big engines like that on a 145 pump so it's not that the pump can't handle it. The 140 pumps are slightly heavier because they use a 144 pump with a thick wear ring and stator section so you have a couple pounds in extra metal.

There have been lots of debates on this and the only thing that everyone seems to agree on is...no matter which mag pump you get, it'll be better than stock.
 
Aircraftsalz

Aircraftsalz

Thrust built Dasa Power
Location
Off site
148 is a great mag pump.... Brian at Thrust has a new mag pump coming out, will be lighter than skat...

Size will be 148

Also we have been playing with setback mags that have 1 to 2in more setback then standard ... A lot to be said about mags...
 
Y

Yamer-Jammer

Location
Mesa, AZ - Flagstaff, AZ - Covington, WA
Hey guys. I am trying to wrap my head around why larger pumps are NOT good for a smaller cc motors? Simple physics (Beroulli's principal) demonstrates that fluid pressure increases the greater the "bottle neck" is, in this case generating more thrust. In theory that greater volume of the pump and smaller diameter of the exit nozzle, the greater the thrust/presure should be. (you can try this my opening your mouth wide and exhaling with your hand in front. Then again, semi-closing your mouth like you are going to whistle and exhale. You will feel the pressure is greater on your hand with the smaller exit diameter). Isn't this the concept that Skat Trak is leveraging with larger pumps such as the 148mm and 155mm?

Perhaps the issue of why a larger pump is not ideal, is due to lack of hp needed to displace the larger volume of water inside the pump?

Any solid ideas out there?

Thanks guys!
 
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Waternut

Waternut

Customizing addict
Location
Macon, GA
Yes that's basically it. Assuming maximum potential, a larger pump provides greater thrust. However, a smaller engine can't overcome the pressure differential, additional drag, etc. to generate maximum potential...or at least not fast enough to do anything a freestyle guy wants. Keep in mind that the 155 pumps are in 250hp+ jetski's with supercharged 4 stroke motors....not an 80hp modded superjet.
 
kevbo

kevbo

Location
dfw
A 701 needs a very low blade angle with 144 impeller. Once pitch requirements excede 17-18 degrees a larger diameter pump should be used. Standups have lower inlet pressure than couches so just increasing pitch to load a powerful engine doesnt work as well. I think stock 155mm pumps would be great with big engines but the whole inlet needs to match. Thats the main reason nobody advocates this, there is no expensive bolt-on part to sell. A used couch pump and some elbow grease doesnt put cash in anyones pocket.
 
BruceSki

BruceSki

Formerly Motoman25
Location
Long Island
This is funny that this thread just came up....We had a talk about this with steveUK at wavedaze about mag pumps and 701's.

The thing with the mag is, IT WORKS. GOOD. end.of.story.

If you find a deal on one thats the "wrong" size, go for it. If you are paying full, brand new price then get the one your motor builder recommends.
 
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JetManiac

JetManiac

Stoked
Site Supporter
Vendor Account
Location
orlando
Everyone has made good points here.

Mag pumps are good for any ski and power level, they just need to be matched to the setup like any other part.

140mm were mainly produced for race skis years ago, but are perfectly fine to use with stock to bb motors and are the cheapest and most commonly available used pumps. Dont think anyone would recommend buying 140mm new because they are the same price as 144mm.

144mm offer the most bang for the mag pump buck because you can have a stock oem pump made into a mag pump. You dont have to buy a one pice billet pump(anything larger than 144mm is billet.)
These pumps are lighter and 144mm big hub skat and hooker props are easily available for swapping pitches for tuning and upgrades. 144mm work well for 701 with bpipe/bolt-on mods up to big bore 780-800.

Mag pumps can be ordered in any mm size 145, 146, 147, etc. But 148mm has become the next 'standard' size so used impellers can be found used for this size. Also 148s work well for 800-up cc motors and lots of testing has been done by many that you can draw from when building your setup.

Having said all that, i predict more and more experimentation with larger pumps as hulls get lighter and motors more powerful. Some of the japanese at world finals were running 155-158mm pumps.
 
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Y

Yamer-Jammer

Location
Mesa, AZ - Flagstaff, AZ - Covington, WA
jetmaniac said:
Stock pump size for XL 700/760 and B2 760...
Click to expand...

So what I am hearing is that Yamaha engineers used a 155mm pump to counter act the greater mass and resistance of a larger body ski, the XL. Hmmmmm... Think of what that would be like in a tiny lil' Superjet! Can we say tennis elbo on both arms! :)

I propose we have a vendor or skat-trak to do a magazine style comparison with techincal specs showing which generates the best thrust. Any takers???
 
kevbo

kevbo

Location
dfw
Yamer-Jammer said:
So what I am hearing is that Yamaha engineers used a 155mm pump to counter act the greater mass and resistance of a larger body ski, the XL. Hmmmmm... Think of what that would be like in a tiny lil' Superjet! Can we say tennis elbo on both arms! :)

I propose we have a vendor or skat-trak to do a magazine style comparison with techincal specs showing which generates the best thrust. Any takers???
Click to expand...

You would need a hull that already has a 155 inlet in order to to get maximum low speed thrust. The main benefit is being able to use lower blade angles and have higher inlet pressure at low speeds. This is more effecient with larger engines than trying to increase load in a 144. A magazine test would be the worst because they say whatever their advertisers want.
 
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Y

Yamer-Jammer

Location
Mesa, AZ - Flagstaff, AZ - Covington, WA
kevbo said:
...A magazine test would be the worst because they say whatever their advertisers want.
Click to expand...

True. However, what I was thinking is an un-biased third party perform the comparison; or, have the article scholarly reviewed. (Which means having a professional in that field with HIGH credentials check it for validity, and edit as needed). If I saw a magazine with this on the front, I would buy it... so would many others.

If a motivated person were to contact Skat-trac and ask for a 144 pump and a 155 pump to do a published review, chances are that the would send the pumps out for free or close to nothing. (The brand recognition / promotion that would follow the article would outway the cost of them sending out two free pumps.) We used to do this in marketing class in high school, u would be surprised of the free stuff you can get from companies by doing shows, events, articles, etc.

Just an idea...

Kevbo: Sounds like you are stuck on the idea that 155 pumps are not going to work in a SJ. Why so bias? Have you tried one yet?
 
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