ltrs per minute

[durban]

Does anyone know how many ltrs per minute a 70hp impeller would pump say at idle rpm & at 5000 rpm , the way i see it the slower the rpm the less water per minute thks

 

[tx1961whaler]

Re: ltrs per minute

It's more complicated than that, unfortunately. At high RPMs, the impeller vanes collapse and it turns into more of a circulating pump rather than an effective pressure pump. The forward motion of the boat will push water into the pump to make up for it.

 

[durban]

Re: ltrs per minute

if one works out the volume of the impeller housing what ever that volume may be , there must be some sort of mathematical formula to move that volume per\mint .

 

[durban]

Re: ltrs per minute

iam sure you can calculate the velocity of the water with a stop watch from the time the motor starts & time the water when it comes out the motor , now you have 2 figures , volume , & velocity , the other one being ?

 

[durban]

Re: ltrs per minute

its the amount of water in the tube i think you calculate , because the impeller pushes that volume in the tube into the motor & the motor then fills up with all the amounts of volume into the motor , now i know the motor takes +\- 2.3 to ltrs of water .i have increased the water volume of my motor to 3,5 ltrs to keep the exhaust box cooler iam trying to work out what pump to buy for my rad conversion , i have an option of a Davey Creigh 12v pump one that pumps 15 ltrs\ minute & the other 25ltrs \ minute

 

[tx1961whaler]

Re: ltrs per minute

I would go with the bigger pump, if it is not too much more expensive.
You are right, it is only the amount of water going up the tube that matters in the end. You cannot completely control the built in flow restrictions in the motor.
"now you have 2 figures , volume , & velocity , the other one being" -- Pressure