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  1. #1
    Join Date
    May 2003
    Location
    Hampshire
    Posts
    986

    Default Engine cooling water intake

    for, in this case, a Yanmar 1GM.
    I finally succeeded in dismantling the through-hull/seacock/strainer in my boat. The seacock had begun to weep a little around its spindle and the plywood pad associated with the through-hull looked a bit sad. Other than that, there was no sign of trouble, no visible corrosion and no suspicious pink patches. The through-hull had a sort of coarse sieve around the intake to keep rubbish out, although this also made it more difficult to remove flora and fauna which had taken up residence.
    So I could just replace the seacock with one of similar design - the original had given about 18 years of good service and a replacement would not be expensive - and replace the little plywood pad (with some decent marine ply this time, maybe even with a coat or two of primer), give everything else a good clean-up and a close inspection, and reassemble. But before I do this, I seek the collective wisdom of this forum:
    Should I replace the through-hull, just to be sure? if I do, should it be with one of the same type? This would be the most cost-effective solution, and presumable what the boat-builder thought best. Do I need the external strainer, or should I have just a hole as normally seems to be done (but it seems to me to invite a blockage)? Given that the original shows no sign of corrosion, is there any point in using materials other than corrosion-resistant brass?
    There seems to be a white material in the threads where the various components mated. I take this to be some sort of plumbing compound (Boss-white or similar). Is this recommended?
    Should there be an electrical bond between through-hull and hull anode (there was originally)?

  2. #2
    Join Date
    Nov 2001
    Location
    Me: Johannesburg South Africa Yacht: Richards Bay East Coast Africa
    Posts
    7,347

    Default Re: Engine cooling water intake

    When I built my boat I did fit water intakes with an external grill/strainer. At the first pull out I cut the external off so I could clean out the build up of little critters that had almost blocked up the inlet. It also allowed me to anti foul inside the inlet
    Life is too short not to have a sea view
    Distantshaws tinyurl.com/yclt6l68

  3. #3
    Join Date
    Nov 2007
    Location
    Boat Orwell - Me Norwich
    Posts
    8,638

    Default Re: Engine cooling water intake

    I have found external strainers problematic for the same reason as you and Rogershaw. I prefer a conventional open inlet, together with an internal filter before the engine. The external strainers are typically at least partially blocked much of the time.

    The internal filters (e.g. Vetus, but several other makes available) are easier to see if it's blocked, block less easily, easier and faster to clear, and pick up finer weed/particles/critters. Why would anyone not prefer them?
    LM Owners Association http://lmowners.proboards.com

  4. #4
    Join Date
    Nov 2011
    Location
    Sydney, Australia.
    Posts
    5,663

    Default Re: Engine cooling water intake

    An advantage of no external strainer is that you can ream from inside and out and clean the pipe work. You can also attach a high pressure hose on the inside and blast the intake. If you arrange the pipe work carefully - as a straight run - you can ream - in the water from the inside - but you do need a long rod (with a strainer further 'upstream').

    When we dry out - I can walk round the hull and clean out each intake from the outside with a screwdriver.

    We have no external strainers on any of our through hulls and do as Roger suggests (he has some excellent ideas) - antifoul using a little artists paint brush up into the intakes, not that this is totally effective

    Jonathan

  5. #5
    Join Date
    Nov 2001
    Location
    Me: Johannesburg South Africa Yacht: Richards Bay East Coast Africa
    Posts
    7,347

    Default Re: Engine cooling water intake

    I used high pressure air from my dive cylinder to blast some of my skin fittings clear.

    200 Bar will shift quite a lot of crud.
    Life is too short not to have a sea view
    Distantshaws tinyurl.com/yclt6l68

  6. #6
    Join Date
    May 2001
    Location
    North Wales, sailing Aegean Sea or Menai Strait
    Posts
    22,133

    Default Re: Engine cooling water intake

    When we transited the Canal du Midi to the Mediterranean our engine seacock blocked countless times with leaves stirred up from the bottom. I was able to clear these by rodding through the seacock with a brazing rod, sometimes 10 times per day. I was extremely pleased not to have a grille over the inlet.
    Answers to some technical queries at new website http://coxeng.co.uk

  7. #7
    Join Date
    Dec 2008
    Location
    Sweden
    Posts
    1,569

    Default Re: Engine cooling water intake

    Quote Originally Posted by blackbeard View Post
    The through-hull had a sort of coarse sieve around the intake to keep rubbish out, although this also made it more difficult to remove flora and fauna which had taken up residence.
    Don't know if something similar is available in the UK, but I have found this type good for keeping out larger pieces of seaweed, jellyfish and plastic bags etc.
    https://www.hjertmans.se/produkter/v...agssil-3-4-tum
    The grill is made of nylon and held to the outside rim of the DZR brass thru-hull by two small A4 bolts, easy to take off for cleaning (and antifouling) after lift out.
    I have a Vetus type strainer above WL as well, but it only catches the occasional bit of eel grass...

  8. #8
    Join Date
    Nov 2011
    Location
    Sydney, Australia.
    Posts
    5,663

    Default Re: Engine cooling water intake

    Quote Originally Posted by vyv_cox View Post
    When we transited the Canal du Midi to the Mediterranean our engine seacock blocked countless times with leaves stirred up from the bottom. I was able to clear these by rodding through the seacock with a brazing rod, sometimes 10 times per day. I was extremely pleased not to have a grille over the inlet.
    Being shallow drafted we have similar issues when exploring weedy creeks.

    We have a wooden dowel rod for the same task - gal reinforcing wire/rod would also work - all you need is that the rubber hose is long enough to be above water line but not so long as to be 'too' long for the rod.

    Jonathan

  9. #9
    Join Date
    Apr 2005
    Location
    Shropshire
    Posts
    9,011

    Default Re: Engine cooling water intake

    The external coarse screen type has gone out of fashion as it has more minuses than plusses provided you have an internal filter (Vetus or similar) all will be well.
    Also you don't need to have an earthing wire provided the fitting is bronze or DZR.

  10. #10
    Join Date
    Feb 2015
    Location
    Erith YAcht Club
    Posts
    492

    Default Re: Engine cooling water intake

    i removed the old raw water seacock which had a basket type strainer on it last winter and installed a normal skin fitting and inline strainer.
    Current boat: 1988 Jeanneau Sundream (lifting center board)

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