Bilge pumps - do GPH matter for ROV building?

[freezway]

Does the actual motor in the different bilge pumps matter? will a motor from a rule 500 outpreform a rule 360? If so, is it worth it going for more GPH?

[sthone]

I know the pump cases (at least with Rule's) are all the same size between the 500, 750, & 1000's (I'd have to actually double check the size of the impellers) but I think it's the actual RPM of the motors that make the difference in GPH that the pumps put out. I haven't actually split open any of the Rule pumps though so it's pure speculation at this point.

-Steve

[AHarris]

When talking about GPH you can increase the impeller size or you can increase the speed of the motor. If you increase the impeller size you shall be shifting more fluid at the same speed, if you increase the RPM you shall be shifting the same amount of fluid but at a quicker speed.
It all depends on the make of the bilge pump.
As Steve has pointed out the cases are all the same size, I have a 360 GPH pump and the impeller goes all the way to the edge so I am guessing that the impeller doesn't change size in which case the motor has a higher RPM but the only questionable thing I can see is that the power rating doesn't increase.

[thegadgetguy]

We have both the 500gph and 1000gph Johnson pumps on our project, and just by testing them you can tell that the 1000gph pump spins way faster than the 500gph pump, and it also seems to have more torque.

[jaanis]

Man Latvian such pumps pay 80 Ls piece ... I can not even buy one ...