Axial or Mixed flow

[Old Guy]

When I got my Sleek Craft, it had a Jacuzzi YJ pump. I quickly searched and read all I could find on these forums. Naturally, I got an Aggressor Energizer kit and replaced the Jacuzzi. Great move....maybe. I never ran the boat with the Jacuzzi so I have no clue as to it's performance. I still have the YJ intake. I found that no one seems to make a shoe for a YJ. Now, if what I've read is correct, the use of shoe/rideplate modifications has only been done on mixed flow pumps. Why is that, I wonder. Can it be true that no one has tried the same modifications on an axial pump setup?
I got a shoe from Duane and added 1" to the center to make it fit the Jacuzzi intake. I haven't had the time to get intake pressure readings and tune the setup yet, but I hope to get a little done before I run out of season.
When we talk about a "high performance jet pump", we are generally including everything from the "hump" in front of the intake back to the end of the nozzle. The components will ALWAYS include:
1. Loader
2. Mixed flow pump
3. Shoe/rideplate
4. Wedge and or diverter.
Perhaps there is a "High Performance" axial flow pump setup possibility if it also had items 1, 3, and 4 above. As far as I can tell, these goodies only came along AFTER the axial pump was discarded as being incapable of "High Performance"
Did I miss something, or did it really happen that way?
old

[Old Guy]

Seems like a reasonable topic to me. Somebody must have some knowledge on the subject.
old

[LakesOnly]

Old Guy:
When we talk about a "high performance jet pump", we are generally including everything from...front of the intake to...the nozzle. The components will ALWAYS include:
1. Loader
2. Mixed flow pump
3. Shoe/rideplate4. Wedge and or diverter.
Perhaps there is a "High Performance" axial flow pump setup possibility ...Did I miss something?
old Actually, you already answered it...mixed flow pumps are the more high performance pump design. Assuming similar size pumps, I don't believe an axial flow pump can produce the amount of thrust that a mixed flow pump can.
This may be why a greater number of hi-perf parts are available for the mixed flow pumps. (It also may be why there are a greater number of mixed flow pump manufacturers, too.) Without the use of centrificul force, and axial flow pump could never generate more thrust than a mixed flow pump.
So, yes, it was a great move. Don't look back.
LO
[ August 23, 2003, 09:52 PM: Message edited by: LakesOnly ]

[Old Guy]

"I don't believe an axial flow pump can produce the amount of thrust that a mixed flow pump can."
If the mixed flow pump is so much better, how come the nasty little PWC's around here don't seem to use them?
The question remains.
If you start with an axial pump, add a shoe, ride plate, loader, wedge and/or diverter, and spend a couple of years tuning it, what do you get. (besides old, tired, and broke)? Is it really true that no one has done this?

[OMEGA_BUBBLE_JET]

I have a jacuzzi yj with a diverter. It was a rare option that was installed by the manufacturer from the factory, so yes there are a few out there. I also have a 'performance' grate for the intake. the grate did improve performance and I can definitely tell a difference in the way the boat rides and handles with the diverter up. this diverter is hydraulic and doesn't produce a monster roost (about 3-5 ft tall) although it is my understanding anything more than this is just strictly for showing off. currently I am running 65mph with a moderate 460 ford in a 2000lb jet(net). I don't really see it getting any better without more hp or a better pump. I have no complaints as of now. I think the answer to your question lies in the limited numbers of axial flows that were built. the yj and golden eagles were the only two that I am aware of and were used in limited quantities. does this make them inferior? I don't think anyone has ever tried to put a large amount of hp to one to see what happens. although they move water at less pressure they still move alot of water. and with the factory stainless tapered impeller and tapered wear ring they are the only pump I know of that can be shimmed without tearing into the pump. I often struggle with wether or not to rebuild the pump with the aggresor kit. I probably will when the time comes due to the cost of replacement parts for yj's and the expense of having a stainless impeller welded and re-cut. for now I am happy with my setup and hope to get a few more years out of it before I need to rebuild. I think you raised a good question though. I attached a picture of my pump with the hydraulic diverter mounted on top in case you are interested.
Omega
http://www.***boat.com/image_center/data/521/523JETPUMP-med.jpg http://www.***boat.com/image_center/data/520/523012431-R1-7A-med.jpg

[Old Guy]

Hey Omega,
Thanks for the reply. From what I have read, I don't know that any other pump would make your boat any faster. Is the performance grate like a loader? When you're going flat out, does the boat get "aired out" and feel kind of loose. Have you ever heard of anyone adding a shoe and ride plate to your kind of setup? That's a nice neat looking diverter on your pump.
I read somewhere that big horsepower will cause an axial flow pump to cavitate. My neighbor's Challenger I/O 502 cavitates also on a hole shot. He still gets near 80 mph out of it.
old

[LakesOnly]

Old Guy:
"I don't believe an axial flow pump can produce the amount of thrust that a mixed flow pump can."
If the mixed flow pump is so much better, how come the nasty little PWC's around here don't seem to use them?
The question remains.
An axial flow pump cannot produce the amount of thrust that a mixed flow pump can. If they could, every drag boat would have one.
I worked for three years as a jet-ski mechanic. Until recently, those engines didn't produce the power output of the larger powerplants jet boats use (proportionally speaking). With the newer 150 hp engines (Kawi Ultra 150, etc.), they can still get away with the axial flow pump due to power-to-weight ratio. Never-the-less, they have major cavitataion problems compared to any axial flow pump I've ever seen. Not near as linear/efficient. Not a poor design the axial flow pump; a different one.
Would accessory components help an axial flow pump? I don't see why not. But could one outperform a mixed flow pump? That remains to be seen.
LO
[ August 24, 2003, 04:59 PM: Message edited by: LakesOnly ]

[Duane HTP]

I have written a two page explination of the differences of axial and mixed flow pumps three timnes now. Each time when I click on post, the computer locks up and I loose it. I give up. Just testing to see if this message will post.

[Old Guy]

Please don't give up Duane. Type, then copy, then paste. Then if it don't work, you can just paste and try again.

[OMEGA_BUBBLE_JET]

Old Guy:
Hey Omega,
Thanks for the reply. From what I have read, I don't know that any other pump would make your boat any faster. Is the performance grate like a loader? When you're going flat out, does the boat get "aired out" and feel kind of loose. Have you ever heard of anyone adding a shoe and ride plate to your kind of setup? That's a nice neat looking diverter on your pump.
I read somewhere that big horsepower will cause an axial flow pump to cavitate. My neighbor's Challenger I/O 502 cavitates also on a hole shot. He still gets near 80 mph out of it.
old Old Guy the grate I have is called a performance grate not a loader. It basically looks the same as the stock grate with 2 pieces of angle iron ramped up towards the top of the impeller. the pump does experience a good deal of cavitation on take off. If I nail it the engine will rev to 6,000rpm before settling down to the 5,300. but only for a brief moment. when I have the diverter up the boat rides fairly dry and is aired out quite a bit. And yes it does feel loose like you can twitch the wheel and responds very well. I would assume I pick up at least 5 mph on the top end by being able to free up the hull. It doesn't ride near as free with the diverter down but it is nice when there is chop or skiers behind you. I have often contemplated what would happen with an energizer kit but at this point it isn't worth the investment when my pump seems to perform as best it can right now. I like the diverter setup also. If you notice it doesn't require a lot of linkage dragging in the water like a berk. Like I said though the setup only allows so much up travel and it does not produce monster roosts like some people like. Overall I am pleased with the performance of the pump. I can pull skiers at 2800-3000 rpm and usually cruise around 3500-4000rpm. I have no idea how my pump would react to more hp but I assume the pump is pretty much maxed out for the setup I have now.
Omega

[beached 1]

LakesOnly:
I worked for three years as a jet-ski mechanic. Until recently, those engines didn't produce the power output of the larger powerplants jet boats use (proportionally speaking). With the newer 150 hp engines (Kawi Ultra 150, etc.), they can still get away with the axial flow pump due to power-to-weight ratio. Never-the-less, they have major cavitataion problems compared to any axial flow pump I've ever seen. Not near as linear/efficient. Not a poor design the axial flow pump; a different one.
Would accessory components help an axial flow pump? I don't see why not. But could one outperform a mixed flow pump? That remains to be seen.
LO This is an excellent answer.
BTW, The Ultra 150 has an Axial flow. wink

[beached 1]

http://www.skat-trak.com/kawasaki_images/kawa_mag.jpg
full stainless steel vanes or you can get in Titanium.
I would think that if there wasn't any mixed flow pumps for the big boats, there would be aftermarket parts available like this for them (axial flows).
The difference is that a PWC (especially on a race course) is skipping accross chop making the pump run dry then loaded, then dry then loaded, etc. Therefore, it makes sense to design a pump like this with 12, 14 or even 16 vanes so that when the pump is loaded, it get's the water in and out ASAFP. This is why PWC impellers are designed to be custom pitched as well. Rather than having to cut the trailing edge (like our berkleys and all), a PWC impeller can be repitched for desired RPM range.It is crucial for the impeller distance to vanes be as little as possible. If a ski needs to turn a certain amount of rpms the pump builder will repitch the leading edge accordingly.
What bakes my noodle is that repitching can be done on the Mixed flow PWC pumps also. Keeping the distance to the vanes, but buy turning down the leading edge would make the pump have to spin more rpms to gain about the same volume. As we all know this is not the case with our Berks and AT's etc. The trailing edge is cut and therefore makes it less efficient. The leading edge stays the same(?) so is it the same idea? Making it less efficient on the tailing edge to get the RPM's desired whci is where the peak HP is made?
I'm just a shade tree hack, but if that's the case then these Berkley type impellers seem a little archaic to me.
Maybe Skat-Trak would consider making pumps for the big boats someday? That would be cool!
[ August 25, 2003, 07:39 AM: Message edited by: beached 1 ]

[Old Guy]

Thanks beached 1
This is what I was hoping for. New information. PWC is often a lot like a dirty word. I live on a lake and on the weekends it is certain that if I go for a boat ride, before long I will encounter a PWC in front of me leaving me wondering which way the thing is going to go next. Maddening..... not the machine, the operator. I have noticed that some of these machines go very fast, and they are very quick.
They may very well represent an engineering marvel. Who knows. I am very interested in how they do what they do. Progress comes from positive thinking, not from negative thinking. My reason for starting this thread is to try to stimulate some NEW thoughts about jet pump design. The dumbest thoughts are those not expressed.

[beached 1]

I am a long time PWCer and fairly new to being a boat owner. I try to keep a open mind as I'm sure many boaters to, but I have on occasion caught myself saying, "F&%king Jet ski! look where you're going!"
I don't think there is much interest in a market for new revolutionary ideas for the big jets. I think because in boating there are other choices. If you don't like a jet, you can choose a I/O, O/B or V drive. PWC's are jets only of course. There isn't any other drive available. So the competition for aftermarket stuff is fierce.
One fear that I have is if or when the PWC mfg's start building bigger and more attractive boats. Sea-doo, Kawi and Yami will be able to build them cheap and this might squeeze out some of the custom boat builders. If someone is going to build a pump like the one I posted above to (to scale of course) it would come from here. I can't imagine a full Ti pump with an impeller that can be pitched on both ends. Mixed flow and could be run dry on the trailer (you can do this with PWC's) sealed greaseless bearings, etc. Built to scale for a boat similar to my Spectra20. Bolt in a big block of your choice and go.
I for one would not like to see this happen. There is something that is soo cool about a custom boat.

[sidewound]

HE HE HE
Your lookin for a way to smoke the neighbor aren't ya OLD! HA! wink
His ride looked good! :rolleyes:
If ya can get ahead of him just raise the roost and plead hydraulic malfunction! LOL!
PEACE MAN :cool:
CESAR