Will this pump work on my motor?

heres the link to the pump
Link
Displayitem.taf?itemnumber=44138

I linked a pic of the pump you originally asked about teamed up with a 4hp engine and using 2" ports.

Rod is right. The different sized ports do change the flow rates and lift. They both increase.

• Like I said

Yes, your 3.5 HP motor will work with that pump even though a 5.5 HP drive is recommended by the manufacturer. You just will not have enough power available to develop the maximum total head of 82 FT while you are running at full speed of 3600 rpm. No pump curve is provided so I am assuming that the pump rating point is 242 GPM at a total head of 82 FT while operating at 3600 rpm.

I would not recommend throttling the suction and I would not recommend dropping the size from 3" to 2", especially on the inlet. You will be working against yourself if you do.

You'll have enough HP available for full speed operation if you don't restrict the discharge very much, certainly will do fine with a free discharge at 242 GPM, if your usage plans will permit a free discharge. Plus, you can always decrease the speed (I am assuming an engine drive here) and thereby reduce the flow, head and required HP from those at the pump rating point.

Rod

Drop the pump ports down to 2"inlet and 2"outlet and enjoy your pump.

Cliff and Frazier just got a little worked up on your question.

You are correct. Generally speaking, one should never throttle the suction side of a centrifugal pump. The use of a throttle valve is to adjust the system performance characteristic to force the pump to operate at a different point on it's performance curve than it otherwise would. A centrifugal pump will always operate at the point where the system curve intersects the pump curve. A throttle valve is a means to adjust this intersection point. Throttling the suction side will only tend to starve the pump, and, as you say, cause undesirable cavitation.

Horsepower is proportional to the product of flow and discharge pressure at any constant speed. A decrease in either without a corresponding increase in the other will result in a net lowering of the hp requirement. Similarly, a decrease in operating speed, without any other system changes, will result in a decrease of both flow and discharge head.

Rod