redesigning engine compartment for non-marinised engines?

Discussion in 'DIY Marinizing' started by Squidly-Diddly, Sep 23, 2009.

  1. Squidly-Diddly
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    Squidly-Diddly Senior Member

    What sort of design changes or added extinguishing equipment would be needed to be able to use standard auto engines from a junkyard in a boat.

    I'd like to eliminate ALL changes and even use standard automobile radiator cooling if possible....just because auto engines can be had for free with a little investment of labor.

    Where is a good overview of the differences between auto and marinised engines and the reasons for the the differences?

    Is fire the main concern, and the reason for the water cooled exhaust?

    I've had a car fire that started from oil leaking from the head gasket onto hot exhaust manifold. It started (or got big) AFTER I shut off the motor and walked away.
     
  2. narwhal
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    narwhal Junior Member

    Water cooling of the exhaust is not necessary; look at the dry exhaust systems used on many commercial fishing boats. I wouldn't think seawater cooling is necessary either, as many boats cool their engines with the coolant separated from seawater by means of a heat exchanger, which is all a radiator is, a heat exchanger using airflow to cool the engine coolant. So I guess the big requirement would be sparkproof electricals, and you may be able to buy those parts separately to put on your junkyard salvage engine.
     
    Last edited: Sep 23, 2009
  3. Squidly-Diddly
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    Squidly-Diddly Senior Member

    most private gasoline boats require water-cooled exhaust

    and I think that is the major problem with using car engines.

    Jet-skis have water cooled exhaust.
     
  4. hoytedow
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    hoytedow Wood Butcher

    What do you mean water-cooled exhaust? I thought the water was just to muffle it. Otherwise send it to the air, muffled. You'll need a marine alternator, though, for the spark issue.
     
    Last edited: Sep 23, 2009
  5. marshmat
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    marshmat Senior Member

    I'm not aware of any mandatory requirement for water-cooled exhaust. Dry exhausts are quite common. The water muffles the sound and keeps things cool, which is often simpler than having to heat-shield and insulate a 1000-degree pipe and muffler; since most boat engines are pumping raw water anyway, wet exhaust is often a logical solution.

    Spark-shielded marine alternator, starter, etc. would definitely be a good idea, along with a proper marine flame arrestor in place of the automotive air filter.
     
  6. tom kane
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    tom kane Senior Member

    trywww.shareaproject.com/pages/projectThumbs,p,9,00.html
     
  7. ben2go
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    ben2go Boat Builder Wanna Be

  8. CDK
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    CDK retired engineer

    Assume you want to install a used 100 Kw (140 hp) engine in a boat without marinizing it.
    The engine will deliver 25 Kw of mechanical energy to the shaft and 75 Kw of thermal energy you'll have to get rid of one way or the other.

    Imagine a cupboard with 35 electric 2 Kw heaters and no thermostat. With the door closed, flames leap out in 2 minutes.
    Redesigning the engine compartment is no option: you have to " design it away". The engine has to stand on deck, with a DANGER! HOT! warning sign near it.
     
  9. pistnbroke
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    pistnbroke I try

    now just explain that to me CDK if its shaft output is 140 hp (100kw) how has it gone down to 33 Hp (25 kw) .........and I thought most of the surplus heat went down the exhaust ....
     
  10. CDK
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    CDK retired engineer

    Pistnbroke, you are right, I should have had coffee first.

    The 100 Kw engine produces 100 Kw at the shaft plus 300 Kw heat, 100 Kw through the exhaust, 200 through cooling and radiation.
    So it's not 35 heaters in a cupboard but 100.
     
  11. TeddyDiver
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    TeddyDiver Gollywobbler

    A seawater pump to get cooling water (instead of air in cars) Some have used copper pipe around exhaust manifold, a liquid/liquid heat exchangers instead of a radiator and as oilcoolers for both for the engine and the gearbox. And a spark protected ventilator too..
     

  12. tom kane
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    tom kane Senior Member

    A very important consideration is supplying cool dense air to your carb or you will loose a surprising amount of power.
     
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