SoCal Jet Boats
Tech Talk => Engine Mechanical / Electrical => Topic started by: speedymopars on September 12, 2008, 11:55:29 AM
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OK, say you have a worn or sloppy clearanced pump, nothing too bad just the normal been around a while type pump on a 50-60 MPH WOT type hull / setup. You totally go through it with a stuffer, etc. (keeping the same cut) what kind of MPH gain are you going to see on the top end? 5 mph? 10 mph? 30 MPH? ... Usually the only cure for performance is more HP :-)
The talk of HP and jets made me start wondering best case what are you going to see. A sloppy jet is going to let the engine rev more, potentially allowing the same water CFM out the back in theory (though I don't know if that theory holds up)...
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On just a pump rebuild I saw 300 less rpm's and somewere around 3 mph gain. I have yet to install my loader. When I do I'll let you know the diffrence.
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Marcs repy is pretty typical of what happens after a rebuild . Drop in RPM's because the pump is loading better and as a result more MPH . Depending on how bad a shape your pump is in , you'll feel the diffrence all around .
-beerjet-
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with the stuffer and all you should also see an appreciable bump in acceleration. Better efficiency equates to faster acceleration in jets better than any other drive system.
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X2 on all counts, won't get a huge increase in top speed, may get a bit more "bite" out of the hole, reduced RPM, but beyond that I wouldn't expect too much.
On the stuffer, it literally just makes the pump more efficient, most times help, not hurt, but heard horror stories, nothing serious though.
A bunch of power won't neccisarily make a huge speed gain either, everything needs to be upgraded to work with each other, think of a 600 HP big block but a worn pump and engine makes best power at 6500 RPM, wont work. Build the pump to the motor and the motor to the pump, that being said, if your cards are played right, build the pump and get the boat working with less HP, then when you get the HP, should work well.
GT
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Wouldn't this have been better suited for the "Jet Pumps" section of SoCal. ;)
Why do you necessarily want to go with the same impeller cut? I'm going to assume A cut. How much HP is the engine? A different cut "might" help it out a lot. Especially, if you don't have a lot of HP.
Good luck. :)
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Wouldn't this have been better suited for the "Jet Pumps" section of SoCal. ;)
Why do you necessarily want to go with the same impeller cut? I'm going to assume A cut. How much HP is the engine? A different cut "might" help it out a lot. Especially, if you don't have a lot of HP.
Good luck. :)
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(https://www.socaljetboats.com/cpg/albums/userpics/10034/dunno.gif)
-beerjet-
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Wouldn't this have been better suited for the "Jet Pumps" section of SoCal. ;)
Why do you necessarily want to go with the same impeller cut? I'm going to assume A cut. How much HP is the engine? A different cut "might" help it out a lot. Especially, if you don't have a lot of HP.
Good luck. :)
Yep - I was in the read posts since last visit mode, and it put it here.. My bad... Maybe Brad can move if needed.
I have an A cut now - and my pump isn't tight, but it isn't really worn out either. I just rebuilt it so it has a new wear ring and seals, but there is a tad bit of clearance where a stuffer would go and the impeller isn't as tight as a new one would be.
In the future, I'll probably rebuild it and go through it - but I need to know the cost performance ratio. I'd hate to spend a grand on going 1 MPH faster.