Raw intakes, exhaust and other thru hulls on Fiberglass Hulls

Discussion in 'Boat Design' started by ChrisN67, Dec 25, 2008.

  1. ChrisN67
    Joined: Jan 2008
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    Location: Kuwait

    ChrisN67 Senior Member

    Just a quickie.....input appreciated.

    I am re-plumbing a fiberglass hull using flanged seacocks with Silicon Bronze thru bolts. This works fine for thru hulls without integrated water pickup scoops.

    But the main engine raw water pickups require scoops. I am thinging the only way to get a thru bolted seacock mounted with a scoop is to first install a flush thru hull then cover it with a strainer grate. Am I on the right track? Any ideas? Thank you.
     
    Last edited: Dec 25, 2008
  2. FAST FRED
    Joined: Oct 2002
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    Location: Conn in summers , Ortona FL in winter , with big d

    FAST FRED Senior Member

    Your idea should work , but why the outside strainer?

    With an internal strainer it is far simpler to loose jelly fish , plastic trash and "Stuff" that hets sucked in.

    For every boat maint , underway is a prime.

    For an engine in the sizes made the Y strainers get my vote.

    Most can be cleaned , without tools , in a few seconds.

    And in an emergency can be cleared by removing the hose and using a broom stick.

    Key in all grp is to seal the edges (epoxy) before installing goop, bolts or thru hull.

    FF
     
  3. fleetwing
    Joined: Mar 2008
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    Location: Kuwait, via D.C, Rhode island

    fleetwing sea salt

    Stay with what works the out side strained, and there are special raw water intakes for thru-hulls purchased at any marine supply store... since , the engine is so large, they need as much assistance to get the water in on the cooling system. bronze , with the the outside strainer is you best bet, and it reduces the stress on the raw water pump....
    elementary....and use a good sealant like 5200 , since epoxy will not bond to the bronze....
     
  4. Frosty

    Frosty Previous Member

    How big is the engine/ engines and at what speed do you expect to get, planing or displacement?
     
  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

    .and use a good sealant like 5200 , since epoxy will not bond to the bronze....


    NO NO NO

    Sorry for the confusion , the raw edges of the glass should be sealed as a primary step.
    Then after the epoxy is well cured the seacock/thru hull should be installed.

    I prefer a thin gasket or block of wood to match the flat bottom of the sea cock and REMOVEABLE goop. 4200 can be seperiated with out a sledge , 5200 is glue "forever" by design .

    The thru hull fitting should be screwed into the seacock after the seacock is fitted.There are scoop type thru hulls should you need the style.

    Here Dolphinite or similar really EZ to remove should be used , as many gov agencies will require the thru hull to be removed & inspected ,but the seacock is usually simply checked for free movement.

    Nothing on a boat is Forever, plan on EZ inspection and replacement.

    FF
     
  6. fleetwing
    Joined: Mar 2008
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    Location: Kuwait, via D.C, Rhode island

    fleetwing sea salt

    From what I recall the boat has two 6ly yanmar Diesels, is was an Intrepid 337 that was extended 21 inches, at the transom to accommodate engines vs outboards , the boat is a Planning hull for and has a step as well,
    The hull already has the holes for the seacocks,,,
    yes Dolphinite should be used, the boat has 1 liter strainers for the raw water intake....
    I do agree with easy inspection and removal ...

    in all actuality the thru-hull should be what the engine manufacturers recommend.
     
  7. Frosty

    Frosty Previous Member

    I gont like scoop with strainer types, they are difficult to anti foul and offer considerable drag. I prefer the normal type and I schamfer the leading edge to get a good flow. A sea cock on the inside and I then raise the pipe to the water line or just above there I would fit a good plastic seawater strainer.

    With that configeration you can rod out any major blockage, you can also open the strainer and freshwater flush the engine.
     

  8. ChrisN67
    Joined: Jan 2008
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    Location: Kuwait

    ChrisN67 Senior Member

    Thanks for the advise Frosty.

    I went ahead and sealed the edges with epoxy (MAS). Unfortunately the hull thickness was over 2.5" so with the addition of a 1" COOSA BLUEWATER 26 Backer board; I needed to use and extra long 5" Buck mushroom with a strainer/scoop cover seperately.

    If using a flanged seacock, it turns out that you MUST use the configuration descirbed. Otherwise you could not get the thu-bolt for the flange do to the obstruction of an integrated strainer/thru-hull.
     
    Last edited: Dec 31, 2008
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