oakleyb
Well-Known Member
Does it matter if the raw water intake hose is lager in size from skin fitting to strainer than the hose that goes form the strainer to the impeller housing.
Thanks
Thanks
Raw Water Hose Size
- Thread starter oakleyb
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nigelmercier
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I know very little about fluid dynamics, but I would guess that it would not be ideal.
NorthUp
Well-Known Member
Not a problem.
edit- within reason, and assuming the engine pump is close to the waterline, not having to lift water to prime to a silly height..
edit- within reason, and assuming the engine pump is close to the waterline, not having to lift water to prime to a silly height..
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pvb
Well-Known Member
You're right that it's not a problem, but the size of the hose makes no difference to the amount of "suck" needed to prime to a given height.
oldbilbo
...
So what's optimum? Strainer about level with raw water pump? A bit higher? Lower? Reasons....?
vyv_cox
Well-Known Member
Vetus suggest a minimum of 150 mm above, I think. Much lower and there is a risk that it will be below water level, so flooding could result. Having it above provides a reservoir that assists pump priming.
nigelmercier
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I'm pretty sure that is wrong. Imagine sucking through a straw, now connect the end of the straw to a 1m diameter inverted funnel and try to suck through it.
pvb
Well-Known Member
You may not believe it, but it's very basic physics.
prv
Well-Known Member
I guess you have to define the question a bit more precisely. We started with "amount of suck", which is hardly good physics
To lift water up the funnel, I think I'm right in saying that you will have to suck a much larger volume of air, but the amount of pressure differential you create will be the same. Is that "more suck" or not? Could be argued either way.
Pete
KREW2
Well-Known Member
I shall watch this thread with interest.
The inboard side of the skin fitting on my boat had a reducer on it. This reduced the size of the hose connector from 5/8ths to 1/2 an inch. The sea water strainer and engine fittings were all 5/8ths.
All the hose was 1/2 inch, obviously heated, and stretched to go over the 5/8th connectors on the engine, and strainer. I had engine overheating problems at continued use of over 2000rpm,
changed all the hose to 5/8ths and it seems to be sorted.
The inboard side of the skin fitting on my boat had a reducer on it. This reduced the size of the hose connector from 5/8ths to 1/2 an inch. The sea water strainer and engine fittings were all 5/8ths.
All the hose was 1/2 inch, obviously heated, and stretched to go over the 5/8th connectors on the engine, and strainer. I had engine overheating problems at continued use of over 2000rpm,
changed all the hose to 5/8ths and it seems to be sorted.
VicS
Well-Known Member
It will take a hell of a lot longer to suck all the air out of an inverted funnel but if you are sucking the water up to the same height the pressure reduction necessary will be the same in both cases.
Basic physics as said
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VicS
Well-Known Member
Your trouble was almost certainly that the hose used was too small.
The original question was whether a larger diameter hose between inlet and strainer will matter.
No it wont unless if any of this is above the water line in which case it will take very slightly longer to "suck out" all the air.
KREW2
Well-Known Member
Your right Vic, I must pay attention in class.
Glad to know I did the right thing by changing it. Must have been one lazy thick person who couldn't be bothered to source the right size of hose.