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Old 03-06-2015, 12:47   #1
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Join Date: Jun 2013
Location: Phila, PA
Boat: Prout Quest 31
Posts: 18
raw water intake from external hose?

I have only 1 thru hull that I use on my 31' Prout catamaran, its for the raw water intake on a yanmar diesel that resides outside the cabin high above the waterline. This thru hull valve needs replacing.

If the engine can draw water out of a bucket on deck why can't I run an external hose below the water line at transom?

I could remove the thru hull altogether and not worry about the extra hole in my hull. Does the thru-hull intake benefit from extra pressure by being forced 2 feet below the waterline? wouldn't that pressure be equalized at the waterline anyway?

If the stern rises enough to allow a little sporadic air intake would that hurt the engine?

I could open/close this eternal intake from the helm instead of having to climb down into the bottom of the boat every time. And if I forget to close it - so what!

jvolpehoo is offline   Reply With Quote
Old 03-06-2015, 14:25   #2
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Join Date: Nov 2014
Posts: 390
Re: raw water intake from external hose?

There may be a couple of reasons for remaining with the original thru- hull location:

-extra length of hose run for the water pump to pull thru...this might cause too much depression at the pump inlet....depression at the pump inlet can cause impeller blades to flex too much resulting in early failure ( this happens with saildrives with blocked inlet slots)

-occasional possibility of sucking air if the stern lifts....if the hose gets too much air, the pump may loose its prime, especially if the impeller is a bit worn

- frequently debris such as weeds and grass float on the surface but are less prevalent a foot or two under the surface....there is more chance of hose and strainer blockage with a pickup close to the surface

DougR is offline   Reply With Quote

raw water, water

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