DIY keel cooler thru hull

Discussion in 'Diesel Engines' started by Sloughfoot, Aug 15, 2019.

  1. Sloughfoot
    Joined: Aug 2019
    Posts: 1
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    Location: North Carolina

    Sloughfoot New Member

    Hi all, new to the forum in a way. I have been reading as a nonmember for some time and have gained some great info. Thanks for that.
    I've been given a good little Perkins 103-07 that came out of golf course equipment. It has 700 hrs on the meter.
    I want to put it in my sailboat 27ft 8,500lbs. I have a good gearbox off of the original ferryman that came in the boat as well as the prop and shaft. I've already yanked the old engine out , threw it out and slapped a 9.8 Johnson on the stern. It sucks! Just enough propulsion to get you in trouble but not enough to get you out.

    So after much research I've came to the conclusion that I could put a keel cooler and dry stack the exhaust. I was thinking of building the cooler from 3/4 copper pipe, soldered joints. But how the heck do I pass through the hull? Somehow I need a waterproof coupling that can be tightened against the hull like any other thru hull that can be purchased or made from copper so it can be soldered to the cooler copper.
    I've searched the web with no luck for a solution, does anyone know of anything?
  2. Deering
    Joined: Feb 2005
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    Location: Juneau, Alaska

    Deering Senior Member

    I would be wary of using copper in saltwater. Corrosion will be an issue. You really don’t want your coolant replaced by saltwater when the copper pipe fails. Copper isn’t that strong either.

    You could do it first class with an external purpose-built bronze keel cooler. That would come with all of the necessary through hull fittings. It would also be $$$.

    You could go with a bronze plate or tube heat exchanger mounted inside the boat. That would only require a couple standard through hulls. It would also require an additional pump for the saltwater.

    I’m sure there are others on here with more experience that can recommend low-cost options.
  3. Lepke
    Joined: Sep 2015
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    Location: Oregon to Alaska

    Lepke Junior Member

    When I was a commercial fisherman, most boats were wood, many people made their own keel coolers from copper pipe. It has to be protected with zinc or aluminum against electrolysis. Usually there is a shaped nose, a wood block that protects the front of the cooler from larger debris. There were commercial thru hulls that included a thermostat and a diverter that cycled some coolant back to the engine when operating temp had been reached. That way there is always a flow thru the engine. You may need to make a bypass that remains open when the engine thermostat is closed. 1/4" would be enough on your engine. Usually plumbed from where heater ports are. Some systems had a restrictor valve instead of a thermostat. Some made their own thru hull by soldering a large copper washer to copper pipe. Washer was bedded and fastened to the hull and a valve on the inside for emergencies. I had a copper pipe keel cooler on my boats. It saves having to deal with a 2nd pump and rubber impeller. I never had a problem and never heard of another fisherman that had a copper pipe failure.
    One issue is idling a long time at a dock in warm, still water. The cooler heats the water around it and eventually the engine doesn't get enough cooling.
  4. Milehog
    Joined: Aug 2006
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    Location: NW

    Milehog Clever Quip

    A dry stack on a sail boat?
  5. BlueBell
    Joined: May 2017
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    Location: Victoria BC Canada

    BlueBell . . . _ _ _ . . . _ _ _

    You can run it straight up the mast!!
  6. Milehog
    Joined: Aug 2006
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    Location: NW

    Milehog Clever Quip

    Who doesn't want a hot, noisey mast oozing oily soot out of every fastener? You can tell people that the patina on the sails is traditional too.
  7. Magnus W
    Joined: Nov 2017
    Posts: 147
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    Location: Sweden

    Magnus W Senior Member

    I would run the pipe through a normal through hull fitting with a hose on it. And then clamp the hose around the pipe (above the wl) kind of the same way as you run shifter cables through the shield on out drives. Simple, easy to repair and maintain and basically fool proof.

    But I second the opinions about dry exhaust. I have it in one of my boats and it's a pain sometimes (and it's a fairly large aluminum work boat) – noisy, smoking and HOT. Keel cooling is nice and you don't have to bother about heat exchangers. But if I were you I'd install an electric sea water pump for exhaust cooling.
  8. goodwilltoall
    Joined: Jul 2010
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    Location: nation of Ohio

    goodwilltoall Senior Member

    I put a copper pipe onnside of keel. Engine is 30hp. 20 foot of 7/8" or 1" was determined to be the right amount of cooling area for my area (it is posted on a past post). I embedded a female screw on fitting w epoxy into hull, then soldered male w elbow fitting, which I think was then teflon taped. The pipe runs 10' first, does a loop, then enters back in w same type of fitting.

  9. goodwilltoall
    Joined: Jul 2010
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    Location: nation of Ohio

    goodwilltoall Senior Member

    Used copper u straps w bronze fasteners then overlaid them w a generous amount of jb weld which was shaped for easy water flow. Used a bigger amount at loop which seems if an object would strike, it would nicely deflect. Use the heaviest copper, i think k pipe.

    A 90 degree strike could possibly cause damage.

    Still have to try it out. The engine is a Sabb which has a second pump built inn to allow seawater cooling, depends on how much noise it makes
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