Yamaha Jet pump all-stainless wear ring assembly

[PSG-1]

As far as I know, these units are made to OEM spec bolt patterns, so, it should bolt right up to your wear ring. Another difference, besides being made of SS, is with the additional 6 vanes, which help straighten out the turbulence. I think the vanes also have a little more 'kick' to their leading and trailing edges to help with this.

[amk]

I asked a jetski guru the 12 vane is better for bottom end pop but will shed a little top end. For top end a bigger impeller pitch is the way to go if it can turn it.

[bellman]

I asked a jetski guru the 12 vane is better for bottom end pop but will shed a little top end. For top end a bigger impeller pitch is the way to go if it can turn it.

I've been VERY involved in race gas, stroker, MSD, Skat pump, etc...standup jetskis for many years. IMO, the guy you talked to is mostly right. The only thing I'd disagree about is the top end loss. With the right prop, EVERYTHING is better with a mag pump. There are several variations. Vane count, size, and setback/non setback. By far the most common/desireable pump is the 12 vane setback. Setback pumps move the stator and prop rearward 1 inch, but require a setback shaft. This isn't much of an issue with jet Jon's since you're installing the pump assembly/cavity and motor mounts anywhere you want them. Between mid shafts and driveshaft lengths you can make almost any configuration work. Almost all yamahas use OEM 144mm pumps, with the exception of a few 760 sit downs and all of the larger motors. Interestingly, until you begin to make HUGE HP, nearly all 701/760 based boats use a 140mm mag pump in place of the stock 144. The stator vanes on a mag pump are stainless and can be be made thinner and straighten the water more gently, allowing for more nozzle exit velocity. There are a few "bastard" 8 vane pumps out there and a fair number of 14 vane pumps, but most are 6 or 12. Either is so much better than stock that it is almost impossible to describe the difference. Think of John Force on his huge wrinkle race slicks compared to him running the same race car on cheap street tires. The difference is that great (especially as you increase power). The nice thing is that the trend in skis is HUGE(1500ish cc twins) motors that actually need bigger pumps. That means that there are far more 140's to be had on EBay for better prices. Even the 6 vane is VASTLY better than stock. With the 140, it requires the uses of a 140mm wear ring also. Skat bores the stock 144 wear ring and installs the smaller dia SS ring. The stator is installed the same way. SS stator installed in a bored stock stator housing. A used 140 will almost always come with the wear ring since it has to be used with that pump. They're also subject to corrosion issues, but the stainless ring breaks the aluminum, rather than the other way around as usual. The good thing is that Skat will install the wear ring or stator in another bored OE housing for about $100. If you happen to buy one new, the best thing to do is buy a chipped up stator and swollen wear ring and send it in to Skat to have your pump built. It'll save you several hundred dollars. I'm on the home stretch on a Tracker 15/42(?) jet Jon conversion (ill post pics when done) that's using a Skat setback 12 vane 140. Luckily I have 5 or 6 props to play with, but so far my experience is that you can run a much taller prop on a flat bottom Jon boat than you can on a ski. The Jon boat is a skipping stone almost the instant you touch the throttle so it's much easier to push. I've normally run a 13/19-21 on most of my skis (65 mph) but I'm starting out with at a 15/22 on this boat. The motor is just a stock 760, but will be running MSD total loss ignition, a bit more compression, a dried out stock pipe, and the mag pump. It should make a bit over 100 HP, so it's nothing crazy and can run on 50/50 AV gas/pump gas. With the right prop and nozzle diameter(stock is 81mm-most people bore the exit nozzle to 83-85mm) cavitation is a thing of the past and you'll be able to drive right through whitewater with no slip or spin. I'll see if i can get a few pics of the mag pump to post so the difference can be seen. Sorry for the dissertation, but a good mag pump setup is really almost too good to be true....except that it is. Hope that helps.

Charles

P.S. Regarding the all SS aftermarket wear ring, I'd personally buy a used OEM on EBay for next to nothing. They're a dime a dozen and usually really bad corrosion is associated with saltwater boats. I'd also personally stick with Skat props. Solas props are Chinese and use inferior stainless. That said, their mag pump copy isn't bad, but the base of knowledge for props, nozzles, etc. is far smaller.

[Jim]

Great thread gentlemen!

Learning a ton!

[CedarRiverScooter]

Me too!

Bellman - can you give any advice on Polaris 148MM Modular pump upgrades?

[PSG-1]

Bellman explained it better than I ever could!

BTW, welcome to the board!

[bellman]

Me too!

Bellman - can you give any advice on Polaris 148MM Modular pump upgrades?

Polaris are a bit of a weird kind of boat. They made some REALLY good boats and some REALLY bad boats. Actually, I should say that about their motors. I've only worked on a few Polaris boats and they were all 650 & 750 triples. They made really good power for the cc's, but had a number of issues. The biggest problem I've always heard/seen with a lot of their triples is the crank isn't welded and it's so long that it's prone to getting out of phase. A buddy burned several holes in one cylinder's pistons before he got a trued and welded crank. I've got a little experience with the Octane standup which was built as an out of the box race boat. It's a twin that came with a good pipe, mag pump, etc. Was pretty successful in the stock class. The only only thing I remember about the pump in the SL 650/750 was that the pump was better than normal for an OE pump and the way it mounted in the pump tunnel was well thought out and was not likely to leak and suck air/cavitate the way a lot of Yamaha and Kawasaki pump mounts can. Sadly, almost no one works on Polaris (even Polaris dealers) and there aren't many people that know much about performance upgrades for them. He'll kill me for sending you to him, but Randy (formerly Watcon-sold business) was very involved with the Polaris factory racing effort back in the day and could probably give you the answer you need. He's the last of the good guys and probably has more Polaris knowledge than anyone alive. I'll PM you his info. Another VERY good source for parts and info is Jetworks. They've been around forever and have always built my motors. I'm an assembler/tuner; not the grinder/cutter. They're no BS and won't ever sell you something you don't need. Impeccable integrity. 949-548-5259. Definitely say Charles told you to call. They have extensive knowledge of every brand of PWC.

Charles

[CedarRiverScooter]

Thanks much! I have the 750 Fuji (blue) engine, rebuilt the fuel system, & it has run great all summer. The pump has eaten rocks & could use some love.

[amk]

Thanks for that post that's exactly what this forum is for.

[bellman]

Thanks much! I have the 750 Fuji (blue) engine, rebuilt the fuel system, & it has run great all summer. The pump has eaten rocks & could use some love.

With all my skis I've always been fanatical about rinsing out the pump after beaching and have managed to keep my pumps and props really mint. The jet Jon will mainly be a bow fishing boat also used for bass fishing. Luckily the rivers I bow fish are rivers I've paddled for years and most of the gravelly stuff that eats pumps is avoidable. The whole jet project is a result of what bow fishing under dams in giant rocks does to 1979 20 HP Mercury motors. [-X I also opted for trim instead of reverse so I can keep the bow above the water in wave trains in rapids. It's a cool story, but I can tell you for sure what happens if you let your bow get swamped with about $4000 worth of bows, rods, tackle, etc with you. It involves a lot of swimming and is a funnier story later than it is at the time.

[amk]

I have the yamaha 760 so your saying go from the oem 144 to a mag 140? Skat offers a 144 mag. And your also saying get the set back?

[bellman]

I have the yamaha 760 so your saying go from the oem 144 to a mag 140? Skat offers a 144 mag. And your also saying get the set back?

I always used 140's, but was curious about how a 144 would work. A friend of mine was sponsored so I was able to get a complete setback 12v with Skat driveshaft for a bit under 1G. After playing with it for a summer, we all agreed that it worked about the same as the 140. Our base of knowledge (props) for the 140 was so much better and between us we have so many different prop/nozzle/cone options to try I decided to sell it and stick with the 140. I'm sure I could have gotten the 144 to work a bit better than it did, but I would have spent hundreds trying different props to get there. A 144 prop for a stock pump doesn't work in a mag pump so it would have been expensive. Props can be repitched, with good results, but most of Skat's props start with different castings, so you can only do so much. You can't repitch the root of a prop so if you repitch a 13/19 to a 14/21 you may not have the same thing that you would if that's what you started with. They usually have about three different castings for each pump size. Not many builders know this (a good thing ). Mine always made sure to order props from a specific casting and then he tweaked until they were right. They frequently aren't exactly dead on out of the box. That said, we're talking about jon boats with stock hp and the ultra fine details aren't going to pay the same dividends. These boats started with 70hp and were in the 140-160hp range when finished so every slight detail could make a big difference. From my experience, it takes a LOT of motor to need more than the 140. I'd also get the non-setback because the stator housing uses the same bearing and shaft set as a stock pump. The setback uses one double row bearing in the housing and it takes some minor machining to make an OE shaft fit. For ease of making it all as simple as possible, I'd look for a used non-setback, although I wouldn't hesitate to grab a setback if the price was right. I would Also gladly take a 6, 8, or 14 vane. Any of them are so much better than the stock pump. Whatever you do, DON'T buy anything weird like a one off 147. You'll chase your tail forever trying to get it to work. Just be prepared to do a bit of work (for a setback) if the driveshaft it comes with isn't the right length for your project.

Charles

[amk]

So with a 140 I can run the same intake right. I don't have to change what's pictured?

[bellman]

So with a 140 I can run the same intake right. I don't have to change what's pictured?

You shouldn't have to change anything. Essentially, if you have a boat that an OEM Yamaha 144 pump bolts into, a Skat pump made to be used in place of the OE 144 will bolt in with no mods needed. Even the setback version bolts in directly. It just requires a 1" longer driveshaft. Normally a setback would be ordered with a shaft for the ski model it's to be used with so it's a simple pump swap. The Skat made shaft for the setback is a good bit more money than just installing your stock shaft into a non-setback. For the Yamaha Superjet (yamaha's stand up ski) a stock driveshaft for a Yam Blaster is the same length as the setback shaft for a Superjet. Some guys have bought cheap aftermarket blaster shafts and machined them to work in a sj instead of buying the Skat shaft. The other simple option is to use a mid shaft from another yamaha that will give you the needed overall length. That only applies if you used the OEM midshaft housing to connect your motor to the pump. If I'm not mistaken, Atlantic Jet Sports has all the yamaha drveshaft and midshaft lengths listed on their website so you can find a combo that will work. It all sounds really complex, but it's really pretty straight forward basic mechanic stuff. Hope that makes sense???

Charles

[PSG-1]

Bellman definitely has a wealth of info about PWC's! This is the kind of info that you won't find in manuals.