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joub 01-18-2003 10:54 AM

Sea Water Strainer
My engine sea water strainer is located about 8" above the waterline. After cleaning the strainer, I often lose the pump prime and have trouble getting the system back in operation.

I''ve made inquires as to the height of the strainer in other boats and have learned that some strainers are mounted above the waterline and some are below.

Below the waterline seems good in that you wouldn''t lose your prime when cleaning, but there must be reasons for locating it above the waterline as some are installed that way.

Anyone care to shed some light on the pro''s and con''s of the sea water strainer''s height?



peterpan2k 01-18-2003 07:54 PM

Sea Water Strainer
If you have a seacock that is easy to access then there is a good reason to lower the filter to remidy the effect of air lock. However if you don''t! It could get a bit hairy when the water starts to flood in and you can''t stop it.
On second thought! Your raw water pump impeller might be throughly worn out. I have Jabsco pumps that are at least a foot above the water line and never have a problem unless the impellers are shot. They''re not hard to repair.

thomasstone 01-19-2003 08:05 AM

Sea Water Strainer
Jim, this is the first time I have ever heard of the raw water losing prime. I used to have my strainer about even with the water line then the hose went about another three feet up to the pump which was about 18 inches above the water.I never had a problem. I am refitting right now and have moved my sea-**** to a different place and now my strainer is about the same height as the pump and when I run the motor on the hard with the hose in the bucket in the cabin even lower the pump starts sucking right away. I would check for air leaks or like peter pan said check your impellar.-thomas

Woodvet 09-17-2015 03:15 PM

Re: Sea Water Strainer
I had a dirty rat aboard my boat once...
Came up my dock line and then down the anchor chain.
It did thousands in damage in very little time.
Including almost chewing through the seacock line to the strainer.
If you ever forget to shut off the seacock as some do from time to time. You might find a strainer above waterline an advantage.
Not sure what this extenuating circumstance with the priming is if legit....
Thanks for that info. I will seek that out.
Salt water is not allowed to get on my engine so the thought if the O-ring or the plastic/glass view was to fail, THAT scares the crap otta me! (If strainer is installed below the water line)..
Through hull for strainer is near keel to keep it charging even on a heel and that has it tortured by egress and ingress about the engine. Stay up on the wear on that too...
The bilge pump should take care of any leaks but with some GRP owners the vigil is more lax and may get neglected.

capta 09-17-2015 04:43 PM

Re: Sea Water Strainer

Originally Posted by Woodvet (Post 3032065)
Including almost chewing through the seacock line to the strainer.

Having the sea strainer above the waterline isn't going to make any difference in this case.

capta 09-17-2015 04:50 PM

Re: Sea Water Strainer
I'd be inclined to locate my sea strainer below the waterline, as anytime the pump goes dry (water running back into an air pocket in the sea strainer) it is damaging the impeller each revolution.

Woodvet 10-14-2015 10:12 AM

Re: Sea Water Strainer
I often strain my coffee through my thick eye brows but it gets hairy...
You are so right cap...
SO, lesson learned: strainer is always placed slightly below the water line.
Be sure and close the seacock before clearing the basket...

I had a boat once that spit a small bit of it's exhaust water out on the cockpit sole where it ran down the scuppers. Told me when then raw water was clogged or the impeller was not up to it's task.
Seemed odd till I had some seaweed in my engine intake.
I also heard of hag fish clogging it up as well but that was a fishing boat.
I liked it after that... I figured out you can't always hear the exhaust, and in rough seas I never feel comfortable leaning out to sea...

asdf38 10-14-2015 10:07 PM

Re: Sea Water Strainer
Well it should be said that many strainers don't recommend installation below the waterline because they're not willing to take the liability. Though real life sometimes dictates otherwise.

Woodvet 10-20-2015 01:14 PM

Re: Sea Water Strainer

Originally Posted by asdf38 (Post 3088178)
Well it should be said that many strainers don't recommend installation below the waterline because they're not willing to take the liability. Though real life sometimes dictates otherwise.

One needs no reminders that real life bears no USCG approval or shall the well paid surveyor dole out any positives to the o'mighty insurer. After all it's only a masquerade to disguise death's face just below the water.
It's there...
If you really wanna look...
And its' there -where all laws go out the window. If you're afraid of dying there are no warrantees you can purchase not a hull that can't be found or a sailor that can't be drown... No corner of the earth you can hide...
There are adventurers, and then there are sales persons who know every approach. Boats will break and taxes to take, seems the whole world is on your back.... Oh, but to sail....
Oh' but to sail out there where you need not heed the orders of the uniform or conform to ideals of fashion. But to touch the hem of god and see how the stars are cast and the waves the soon wafts with her mere appearance.
All we know for certain is that nothing lasts...
It never lasts...

overbored 10-20-2015 02:23 PM

Re: Sea Water Strainer
if you loose prime then you have an air leak. if the strainer and all piping are completely sealed it make no difference where the strainer is in the line. it is just a fat section in the pipeline. because it is on the suction side of the pump you can have a leak that will let air in and will not leak water out.

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