closed cooling outboard?

Discussion in 'DIY Marinizing' started by fishon91, Feb 22, 2011.

  1. fishon91
    Joined: Dec 2007
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    fishon91 Junior Member

    im not too too knowledgable on every aspect of an outboard motor, but i got to thinking earlier (thats where i went wrong). an air-cooled mud motor, longatil, is seeming like its too far out of my price range right now. i need to find a 14ft. boat trailer and some sort of motor to get my boat on the water.

    The problem is is that i have spots i need to go way back in the woods and imnot sure yet if i can get a stock outboard in there or not. Ive been wondering lately just how much an outboard can handle. ive seen videos of people running them in mud(which i DO NOT plan on doing), but i think i would be fine with jumping a couple of laid down logs with an outboard at a slow speed to not damage the skeg.

    I was wondering how hard and plausible would it be to hook a radiator up to an outboard motor and make it a closed cooling system so i could run with the prop out of the water for longer and not have to worry quite so much about weeds and junk.
     
  2. fishon91
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    fishon91 Junior Member

    *of course im saying this planning on a free or grealty dicounted radiator, otherwise i would just buy a longtail
     
  3. CDK
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    CDK retired engineer

    Not impossible but certainly difficult.
    You need a belt driven or electric water pump, hoses, an expansion tank and a radiator with an electric fan. Except for the pump, the other parts take space in your boat. And you will only succeed if the construction details of the outboard allow you to completely isolate the engine cooling circuit from the plumbing in the leg.

    A simpler approach would be to construct a water pickup near the surface and use an electric pump with sufficient capacity. The original pump will not survive long with the prop out of the water.
     
  4. fishon91
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    fishon91 Junior Member

    your saying to cut a small hole, or more, on the front of the boat for an inlet? Hhhmmm..... id just be worried then about stumps and randon junk hitting the inlet and breaking something.
    im really just hoping i can find a longtail(9-12 hp) for about $500. im just trying to think of some other solutions and maybe some innovative ideas.
    how long can a small outboard run with the water inlet out of the water and just how easily do they get clogged with weeds?
     
  5. Erich_870
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    Erich_870 Junior Member

    Head over to the The Refuge Forum and get a hold of this guy: 1995 US1

    He's a power boat expert and I've seen him talk about a closed cooling system created by welding a length of aluminum angle iron to the bottom of your boat and turning your boat into a water to water heat exchanger to protect the outboard from mud and debris just like you want to.

    Erich
     
  6. Yellowjacket
    Joined: May 2009
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    Yellowjacket Senior Member

    Part of the problem with changing an outboard to a closed loop cooling system is that the present system dumps cooling water into the exhaust. You would have to figure out a way to collect that water so that it could be recycled.

    In addition, an outboard gets very cool water to cycle through the system. Recycled closed loop water is a lot hotter and doesn't cool as well, so you are going to need to supply more water and flow it faster through the system to get it to work.

    It might be easier to provide a pickup at the transom and plumb it to the existing water pump inlet with a section of hose that would let you pull the motor up and let you get it over the junk. These kind of pickups are often used on high speed V and tunnel hull boats to allow the outboard prop to be run as a surfacing prop and what you need to do isn't all that different from that.
     
  7. Frosty

    Frosty Previous Member

    Ok my turn-- why don't you get an old lawn mower engine and modify that to replace the power head of the outboard.

    Maybe some kind of air boat might be more suitable for the conditions your describing.
     
  8. fishon91
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    fishon91 Junior Member

    frosty: its all about money for me. i would love to build my own surface drive but im in way too bad of a bind to do all that.

    the boat i got is a 14ft aluminum flat bottom riveted boat. i would be leary about welding very much to it especially lengths of angle iron. and then what happens when i hit a stump a little too hard and bend the angle? the thought of that makes it seem like puttin a radiator beneath the boat.. just too risky.

    i kinda like CDK's idea, i'm just not too sure about it yet. i would need a thru-hull fitting and some kind of water filter(or series of filters) that is plenty strong enough to take through kindof thick weeds and over some small stumps. i assume that with an electric water pump it would be ok to take the inlet out of the water for just a second right?
     
  9. CDK
    Joined: Aug 2007
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    CDK retired engineer

    You need something like this in an easy-to-reach location:
    http://www.marineparts-24.de/images/product_images/info_images/1603_0.jpg
    It is solid brass, stumps won't damage it (rocks do). The electric pump can run dry if it is a vane type, an impeller type needs to stay wet. Out of the water for a few seconds never is a problem.
     
  10. slow fred
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    slow fred Junior Member

    Buy an air cooled outboard. Briggs & Stratton makes one.
     
  11. fishon91
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    fishon91 Junior Member

    the briggs n startton aircooleds are just such small hp that it wouldnt even push my boat out of its own way.

    CDK, i like this fitting. Do i need to add water filters further down the line or not? if so, what kind of filters?
     
  12. gonzo
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    gonzo Senior Member

    The leg would end up overheating with dry exhaust. One of the problems with that, is the oil seal will burn. The exhaust needs to be modified, which will create less back pressure. Depending on the design, that will require more modifications.
     
  13. fishon91
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    fishon91 Junior Member

    i could make it where cold water routes through the motor and everythin the same right? im thinking of just relocating the cold water inlet and bypassing the water pump with a remote electric pump.
     
  14. gonzo
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    gonzo Senior Member

    What would that accomplish? If you have to have a radiator on top of the usual cooling system, there is no advantage and a lot of complications.
     

  15. Frosty

    Frosty Previous Member

    Fishon your flat alluminium boat is ideal for an air boat .
     
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