Raw water strainer - Yes or No.

Discussion in 'Inboards' started by missinginaction, Jan 23, 2013.

  1. missinginaction
    Joined: Aug 2007
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    missinginaction Senior Member

    Now that I have the cutless bearing straightened out, I'm ordering parts to finish the engine installation. The application is a 27' (1973) Silverton Sedan that I've completely restored over the past few years.

    1. 302 Ford V8
    2. Warner Velvet Drive
    3. Walter V-Drive

    I have a scoop strainer that is perfectly serviceable. It is this type:

    http://images.jamestowndistributors.com/woeimages/hardware/large/14713.jpg

    After water passes the scoop it travels through a 1 1/4" seacock, through the V-Drive and up to the Sherwood raw water pump. From the pump it passes through a transmission oil cooler ( http://bpi.ebasicpower.com/pc/HEXCS-205-6-C/PLECOOL ) and then into the engine thermostat housing. On exiting the thermostat housing the water splits off to the two exhaust manifolds using 3/4" NPT X 1" hose barb fittings and 1" water hose.

    My question is this. Subscribing to the "as long as I'm assembling this" philosophy, should I add a raw water strainer to the system? The easiest place to splice in a strainer would be between the transmission and the raw water pump.

    Something like this:

    http://www.defender.com/expanded.jsp?path=-1|51|305312|614247&id=1798198

    A second question. I see these pumps come in stainless steel or bronze. It would seem to me that bronze would be called for as the seacock is bronze as is the scoop strainer and the raw water pump. Correct?

    When I disassembled the old system there were a couple of small twigs in the oil cooler, other than that just a couple of small pieces of broken off impeller vane from the Sherwood pump.

    So, what say you? Strainer or no strainer?

    Regards,

    MIA
     
  2. michael pierzga
    Joined: Dec 2008
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    Location: spain

    michael pierzga Senior Member

    Ive never been on a boat without a sea strainer.

    I dont like those strainer style thru hulls...they plug with growth.

    You pump link doesnt work

    When you choose a strainer, if possible pick the largest and one with additional seawater outlets. A common system if for one outlet to be used for a fresh water garden hose so that you can flush seawater from the system or antifreeze the system at the end of the season.

    Blowing backwards thru the sea strainer with fresh water is also a common way to eject jellyfish from strainer and thru hull.
     
  3. midnitmike
    Joined: Apr 2012
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    midnitmike Senior Member

    In almost every system I've seen the sea strainer immediately follows the sea cock thus providing protection to every component downstream from there. Now whether or not you need one is a question that only your service requirements and conscience can answer. If the boat is going to spend it's life tied to the dock then you're probably safe leaving it out. On the other hand if you intend to use the boat for something other then a dock decoration then by all means install the strainer.

    MM
     
  4. missinginaction
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    missinginaction Senior Member

    Thanks for the input guys. Michael, this little service attachment installs right on top of the seacock. I believe that it's similar to what you are referring to.

    http://www.boatersland.com/grossc1250.html

    I could install the strainer behind the valve and before the v-drive. A bit more work but hey, I'm in there anyway.

    Thanks,

    MIA
     
  5. FAST FRED
    Joined: Oct 2002
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    Location: Conn in summers , Ortona FL in winter , with big d

    FAST FRED Senior Member

    For the best installation , yes a strainer after the bolted in tapered seacock is great.

    However ALL the water pumps with rubber impellers will die , some loosing parts as they go.

    Their old parts get into coolers , engines and even exhaust manifolds , and can be HARD!!! to find. Harder to remove!

    For a top notch installation I suggest a Sendure style Y strainer just after the rubber impeller pump.

    New or used , what ever you can find as these are bronze and last almost forever.

    A few seconds and the strainer can be examined to see if the rubber impeller pump is shedding parts.

    Not needed often , but when the impeller lets go its SO! easy to just stick in a spare and not worry about chunks of rubber in your engine.
     
  6. missinginaction
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    missinginaction Senior Member

    You learn something new around here everyday Fred.

    I could install something like this http://www.grainger.com/Grainger/Y-Strainer-6NPX2#
    right behind the raw water pump. Since there is already a basket strainer in the system this little strainer would only be responsible for picking up impeller pieces. Not very expensive, just need a couple of pipe to hose adapters.....thanks MIA
     
  7. Frosty

    Frosty Previous Member

    I would install the strainer as high as the water line so that you can remove the top and probe out any jelly fish or the like without flooding the boat.

    And as I do you can take off the top put a hoes pipe in and flush with fresh.
     
  8. Submarine Tom

    Submarine Tom Previous Member

    No question about it:

    Yes.
     
  9. CDK
    Joined: Aug 2007
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    Location: Adriatic sea

    CDK retired engineer

    When I repowered my boat a number of years ago, the idea to use strainers -except for the scoop strainers- never crossed my mind.
    I clean the scoops with Scotchbrite, not because they really need that, but the boat is on land in winter anyhow.

    Adding strainers would be totally useless in my case. The small engine bay is pretty crowded with two diesels, 3 batteries and a gas bottle, so there is absolutely no place to stand. The raw water hoses from scoop to pump and oil coolers are all on the bottom, to reach a clogged strainer there I would need a dwarf with double joints in his limbs.
     
  10. missinginaction
    Joined: Aug 2007
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    missinginaction Senior Member

    Good to hear from you CDK! I understand your point of view. My boat had no strainer except the scoop when I bought her. Over the years though we have had an increasing problem with invasive weeds. A second issue is this little creature called a Zebra Mussel. These critters are about the size of a fingernail and people tell me that if the larva get into the cooling system they can be a real headache. I figure that for a couple of hundred dollars and an hour or two of my time I can buy some cheap insurance. I have to build the system from scratch anyway.

    Best Regards,

    MIA
     
  11. CDK
    Joined: Aug 2007
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    Location: Adriatic sea

    CDK retired engineer

    As far as I know mussels start their miserable life as almost invisible seeds that pass through anything except a real filter cartridge. I have feared they would settle in large numbers inside the heat exchangers and I contemplated several times to take one apart. What kept me from satisfying my curiosity is the lack of spare parts in case one of the rubber grommets would crack.

    On the other hand, I noticed that they grow mainly in the winter when the water is cold, and of course they need a constant supply of calcium to build their shells, so the environment within engines or heat exchangers probably doesn't suit them. Instead, they have settled in large lumps around my mooring lines, buoys and the bottom of my rowing boat. Many of the shells are already over 2 inches long, but the animals inside are disappointingly small; you must be really desperate to harvest and cook them.
     
  12. michael pierzga
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    michael pierzga Senior Member

    Ive never seen growth in the sea strainer and downstream from the sea strainer, in the Mediterranean. Years ago I stopped antifouling my sea strainer filter because I never saw any growth and the paint closes the water passage holes in the screen filter.

    I suspect that water in the system becomes anaerobic or otherwise not friendly to marine critters.

    Perhaps ships with a constant stream of sea water thru their plumbing are suseptable.
     
  13. FAST FRED
    Joined: Oct 2002
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    Location: Conn in summers , Ortona FL in winter , with big d

    FAST FRED Senior Member

    The Grainger unit might do the job , but the Sendure would have less restriction as it may have 4x or 5x the surface area of screening.
     
  14. missinginaction
    Joined: Aug 2007
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    missinginaction Senior Member

    Thanks again Fred........speaking of restriction......

    I have one more question so I'll try fishing here, maybe someone who's installed these strainers can add a little clarity.
    I'm using 1-1/4 inch water hose running up from the seacock to the water strainer.

    I'll need to buy the strainer and a couple of NPT to hose barb fittings to attach the 1-1/4 inch hose to the strainer.

    I notice that I can use a couple of different strainers. I can use Grocos arg-1000 strainer that uses 1" NPT fittings and use Groco's "full flow" pipe to hose fittings.

    OR, I can buy a slightly larger arg-1250 strainer that uses 1-1/4 NPT fittings and use Groco's "standard flow" fittings.

    The "full flow" pipe to hose fittings mate 1-1/4 inch hose to 1 inch npt pipe.
    The "standard flow" pipe to hose fittings mate 1-1/4 inch hose to 1-1/4 npt pipe.

    I've researched this last night and cannot find any data on the full flow versus the standard flow fittings. Either set up will work with my 1-1/4 inch hose.

    Bigger may be better, so the ARG-1250 might be the prefered way to go but I'm curious is anyone has any thoughts on this.

    BTW here is a graph of the flow characteristics of the strainers. The top graph shows the flow of the 1000 and 1250 strainers.

    Thanks in advance for any thoughts.

    MIA
     

    Attached Files:

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  15. El_Guero

    El_Guero Previous Member

    I think you are asking two different questions.

    However, the flow will NOT be the same if you reduce to a smaller pipe (fitting) and back up. Typically, when plumbing, you try not to reduce pipe size and go back up. There are times you cannot get around that. The fittings you need are not available is the only good excuse I can think of.

    So, I would say the bigger one would keep the size the same.
     
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