brett fiddes

I was looking for some help in verifying whether the water pickup I'm using is going to be large enough




1. engine is 502 or 556 ci Chev BB, it will be N.A. or turbocharged
2. I intend to use mercruiser closed water system, and install larger expansion tank
3. the mercury performance engine sump is 12 litre capacity
4. the exhaust will be sea water cooled to ensure the closed water system cools engine without adding the extra heat from exhaust
5. the external water will be cooling engine cooler, hydraulic power steering cooler, exhaust cooling, and HX cooling
6. Sea pump: was going to use Jabsco crank mount pump, or Mercruiser 46807151, or after market pump. As far as I can make out the Jabsco, and Mercruiser pump output is approx. 25 gallons (100 litres/min) @ 4000 rpm
6. I have used 1.25" claim shell water pickup, ball valve Hose 1.5: (1.25" ID)
7. The claim shell external water pickup is 16" from transom, and 6" off centre

Questions
A. Do I need to modify the claim to remove some of the grate, to increase the flow surface area?
B. will one pickup be sufficient, or do I need to add another pickup?
C. some of the time I imagine back of boat will be out of water, so wondering how the sea pump will handle this?

cheers
Brett
:

F-2 Speedy

Is that the bottom of a strainer the pickup its plumbed to ?

brett fiddes

yes that's correct

F-2 Speedy

mine feed in the top and exit the bottom.... not sure where the filter screen is located in yours

brett fiddes

found a few more pics of the strainer itself
The strainer is cylindrical, water comes up inside of strainer and moves through to outside of bowl

F-2 Speedy

I see, that makes sense now I see it apart, I dont think you will have any issues with water volume but its hard to tell the width of the slits in the pickup

brett fiddes

The slits are 2.3 wide x75mm long = 172mm = 0.266 square inches x 7 slits = 1.86 " (1207mm2)

brett fiddes

If incoming water supply is through 1.25" (32mm ) Dia strainer
Then assuming my calcs are correct 38mm/2 = 16mm Radius
16mm x 16mm x 3.142 = 804mm 2
so looks like it may delivery sufficient water
Perhaps strainer is a little on small size to hold sufficient water, although not sure?

F-2 Speedy

I know guys running 2 stage pumps to large inter coolers and the engine through a single 1.25 hose

brett fiddes

my concern is the claim shell water pickup and whether at speed it will pick up water
I suppose I could increase the size of 2 of the split by removing some of the casting, that should increase surface area by 25%
I wonder if anyone else running these water pickups?