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Author Topic: Wear Ring explanation.  (Read 7347 times)

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Offline Painlesstom

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Re: Wear Ring explanation.
« Reply #15 on: June 29, 2015, 04:31:40 PM »
Already did it Jim, slowed me down. Two things are necessary to achieve speed, power and pump efficiency, both of which are lacking in these boats. In my Jet Jon, at 4500 rpm I am going 25 mph. Manage those rpm's in a Mokai and all you get is 16-18 mph, more from the redesigned ES-Kape hull, but not much.
Tom

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Offline French Broad River

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Re: Wear Ring explanation.
« Reply #16 on: June 29, 2015, 05:12:09 PM »
Had to try it! Agreed on a little harder to turn...but it felt like a little more speed...had to try... >:(

Offline Odie

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Re: Wear Ring explanation.
« Reply #17 on: June 30, 2015, 08:50:03 AM »
I wondered the same thing but some research I did suggests it would probably hurt top speed because water volume is actually reduced. The research discussed reducing the cone circumference within the impeller housing to affect top speed but I would have no clue on how to do that or how to easily revert back if the experiment failed.

Offline Painlesstom

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Re: Wear Ring explanation.
« Reply #18 on: June 30, 2015, 09:15:36 AM »
The principal works provided there is enough power behind the pump. When a Jet ski can bounce off it's 6k rpm rev limiter at full throttle, under load, then there is power to spare there... reducing the outlet diameter would then use that extra power to generate more thrust. We just don't have any excess power to play with... 5000 rpm would be the magic number where best performance would be achieved in my opinion, and we ain't gettin' close to that with these go cart motors.. lol
Tom

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Offline Odie

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Re: Wear Ring explanation.
« Reply #19 on: June 30, 2015, 03:39:39 PM »
By power to spare you mean torque as in immediately available I'm guessing?  5000 does seem unattainable. No grate and the stock kx isn't far from it tho. That is until the heat thing kicks in. Seems to me the grate is the next available option for a bolt on performance gain. Then we open up another wormy can..

Offline Painlesstom

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Re: Wear Ring explanation.
« Reply #20 on: June 30, 2015, 06:37:44 PM »
Spare power in that you can reach the rev limiter while under load, a 200 hp jet ski isn't going to be struggling to reach max rpm.. Using that "reserve" to push the water through a smaller nozzle with that much power behind it would result in faster flow with more thrust. The Subie can't even reach it's "max" rpm as it is, so narrowing the nozzle is just choking it off and you slow down.
Tom

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Offline bizler

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Re: Wear Ring explanation.
« Reply #21 on: July 01, 2015, 04:56:37 PM »
For those who wonder what the result would be if the pump nozzle were reduced to the size of the outlet of the pump, wonder no more...
I built a nozzle choke that attaches to the existing pump nozzle with an opening of 2 1/2". The logic I used was that by narrowing the stream at the same volume output would result in increased velocity.  That might be true, but the narrow stream does not provide as much thrust.  I tested my adaptation on Lacamas Lake today and the results were just as Tom said they would be.  Although the top engine RPMs were the same as with my reverse unit, the top speed was considerable slower. 

After making a test run with the nozzle choke, I changed back to my reverse unit and compared the performance.  Here are the results with the nozzle choke:  The last two are the results of my "normal" nozzle.

Offline French Broad River

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Re: Wear Ring explanation.
« Reply #22 on: July 02, 2015, 12:53:17 PM »
Thanks to everyone's input and discussion on results of nozzle length and reduction. I always learn a lot listening to voices of experience!
New wear ring came yesterday. Put it in this morning. Great product...great instructions....fit like a glove! Thanks Tom!  \./8

Offline Painlesstom

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Re: Wear Ring explanation.
« Reply #23 on: July 02, 2015, 01:57:50 PM »
Thanks to everyone's input and discussion on results of nozzle length and reduction. I always learn a lot listening to voices of experience!
New wear ring came yesterday. Put it in this morning. Great product...great instructions....fit like a glove! Thanks Tom!  \./8

Excellent, glad it was a "Painless" experience! haha Looking forward to the performance update.  >:D
Tom

  >:D    

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