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mudslinger
Joined: 21 Jul 2010 Posts: 40
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Posted: Tue Sep 21, 2010 11:31 am Post subject: loss of RPM why |
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I was wondering why I dropped from 4400 to 4200 when I put in a stainless impeller and new wear ring .,old one was aluminum. 350 kodiak ,sd 309 |
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Will R
Joined: 31 Jul 2005 Posts: 677 Location: NWT/Alberta
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Posted: Tue Sep 21, 2010 11:51 am Post subject: |
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considering its the same cut you just answered your own questinon! its because you went to a stainless from an aluminum (rotating mass increased dramaticly) _________________ When in doubt hammer down! |
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boosted
Joined: 04 Jun 2009 Posts: 378
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Posted: Tue Sep 21, 2010 1:16 pm Post subject: |
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The s.s impellors actually flow different also. _________________ Mark
Lets go back I think we missed one rock! |
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mudslinger
Joined: 21 Jul 2010 Posts: 40
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Posted: Tue Sep 21, 2010 1:54 pm Post subject: |
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Thanks, another question I"ll probably answer:with the drop It seems I lost some performance (speed) although hardly significant still notice it, same pitch as the old one. short of getting a new motor whats a guy to do? I guess 45MPH is about all a guy can expect from the 350 kodiak with the 309 . |
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Kev-o
Joined: 17 Jun 2005 Posts: 625 Location: Sylvan Lake
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Posted: Tue Sep 21, 2010 8:52 pm Post subject: |
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What style of hull are you running and bottom?
Kev-o _________________ Kevin Kipling |
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Arthur Outlaw Eagle Admin
Joined: 28 Oct 2006 Posts: 1654 Location: On the rocks
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Posted: Tue Sep 21, 2010 9:14 pm Post subject: |
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Experienced the same deal....went from 5100 to 4500Rpm! Tough pill to swallow but financially worth it! |
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riverboater
Joined: 10 Dec 2009 Posts: 153 Location: Prince George
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Posted: Wed Sep 22, 2010 1:13 am Post subject: |
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Could you not open up the nozzle a bit to regain the lost rpm? |
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boosted
Joined: 04 Jun 2009 Posts: 378
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Posted: Wed Sep 22, 2010 7:53 am Post subject: |
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You can just cut the impeller down to get your rpm back. If the rpm drop is becausethe impeller flows better than you should be seeing a speed increase at the same rpm as the old one. 3800 rpm was 38 mph now 3800rpm is 40 etc. _________________ Mark
Lets go back I think we missed one rock! |
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mudslinger
Joined: 21 Jul 2010 Posts: 40
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Posted: Wed Sep 22, 2010 9:04 am Post subject: |
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Boat has a 12 degree with UHMW the UHMW runs down the keel as persay . Mark what do you mean by cutting down the impeler, I"m basically a newbie 3rd season with boat but learning real fast if you all know what I mean (nasty rocks!)dam tree! oh ya *%#% KAYAK! but all is good. |
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boosted
Joined: 04 Jun 2009 Posts: 378
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Posted: Wed Sep 22, 2010 11:05 am Post subject: |
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Here is a chart. You can change the impeller to asmaler one by machining it.
H.P. 9.5 9.25 AA A B C
150 2900 3050 3200 3600 3800 4050
200 3200 3350 3500 4000 4200 4450
250 3450 3600 3700 4300 4500 4800
300 3800 3950 4050 4550 4800 5100
350 4050 4200 4300 4750 5100 5350
400 4250 4400 4500 5050 5300 5600
450 4450 4600 4700 5250 5500 5850
500 4650 4800 4950 5400 5700 6050
550 4800 4950 5100 5550 5850 N/A
*THESE RPM VALUES MAY VARY ACCORDING TO HOW YOUR BOAT ALLOWS THE PUMP TO LOAD
HORSE POWER REQUIREMENTS ARE AT THE PUMP SHAFT
so you probabbly have a AA or an A. A s.s AA will take more power to run at 4500 than a Aluminum one will. It usually woprks out to 1/2 a size. Rember when looking at the chart the hp is observed hp not corrected like a dyno number would be. A 330hp is only around 280 observed. _________________ Mark
Lets go back I think we missed one rock! |
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