Diesel Heat Exchanger Conversion to Radiator

Discussion in 'Diesel Engines' started by Christopher McTurnan, Jun 20, 2018.

  1. Christopher McTurnan
    Joined: Jun 2018
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    Location: Newport, NC

    Christopher McTurnan New Member

    This is probably a very worn out topic but this is what I got. So I have an older Columbia 9.6 monohull that runs a Volvo MD6B 10 horse in it. Long story short, 10500 lb boat unladen and 10 hp isn't a good match when you take into consideration wind, current and tides on a bad day. My motors transmission went screwy this past weekend and had to get towed 4 hours to my marina. Older Volvo engines have quite a bit of parts that aren't made anymore and if they are you have to spend an arm or a leg to get them. Marinized engines are overrated.

    I am a diesel mechanic by trade, been doing it for 20 years, and have a design idea. Dry stack tractor diesel, 3-4 cylinder equaling between 20-40 hp, installed on my boat. I have read a ton of forums and literature and it just seems the nay-sayers are just those die hard marinized diesel fans with the money to drop in a new Beta or Volvo. When I read articles and forum posts on how radiators need a constant flow of air for cooling efficiency, go look at older earth moving equipment. Those beasts don't move fast and still maintain a cool operating system. Answer.......alternative air flow sourcing.

    My transom is hollow with a large compartment for access to a couple wires. By measure, I can fit a 3 core aluminum radiator with 12 volt fan system in there. Vent the access cover and utilize the discharge ports already already sitting on the top of the transom.

    Venting the engine compartment would be a bit more tricky but doable via vents built into the underside of the stairs and then exhaust plenums and ducting running out of the transom or other area aft of the cockpit not frequented.

    The whole exhaust system will be double wrapped and ported using a "wood stove" type of setup so as not to damage the hull.

    Cost plus materials:

    Engine-$1200 Kubota 20 hp
    Ducting -$100
  2. gonzo
    Joined: Aug 2002
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    Location: Milwaukee, WI

    gonzo Senior Member

    Any earth moving equipment has the radiator and engine open to the atmosphere. The engineroom in a boat is closed, so the engine will overheat unless you provide enough airflow. The vent area, if you are running a water cooled exhaust will have to be about the same area as the face of the radiator; your discharge ports won't do. If the exhaust is dry, the vent area will have to be larger to account for air cooling the exhaust. A heat exchanger is most likely cheaper, and lot easier.
  3. kapnD
    Joined: Jan 2003
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    Location: hawaii, usa

    kapnD Senior Member

    Many have tried this exercise ahead of you, and I’m not aware of any real successes.
    If it worked, it would be very popular, as it could cut the hell out of the cost of marine diesels.
    Just ran across one in south Florida Craigslist for way cheap! Somebody put a lot of work and dollars into it, and it just won’t sell.
    Cooling on a marine application must be MUCH beefier than on an automotive, truck, or heavy equipment situation.
    Even if you should get enough air packed into the ER to cool everything, what happens when you turn downwind?
    Better include an air conditioner and a closed cabin, oops, another heat source to deal with!
    There is always an unlimited supply of excellent cooling fluid right under the keel, suggest you find a way to utilize that.
  4. Sparky568
    Joined: Jan 2017
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    Location: Northeast USA

    Sparky568 Junior Member

    Let’s not forget about safety either. An oil or high pressure diesel leak spraying a fine mist of fuel on hot exhaust parts combined with gouts of fresh air and you have an engine room that is now an oil burner. Not good. Does this happen often no, but when it does...... A tractor or piece of equipment is easy to jump off of and walk away, not so much on a boat.

  5. Lepke
    Joined: Sep 2015
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    Location: Oregon to Alaska

    Lepke Junior Member

    Radiator cooled engines in an engineroom make it exceedingly hot. Besides making the rest of the boat hot, the air supplying your engine will reduce efficiency because it's so hot. It's probably not possible to vent enough air to maintain a proper temp. I use to run a 100' tug that the company installed a cheaper radiator cooled generator into. It made the engineroom unbearable in a cool climate even though we had 36" fan ducts.
    A better method would be homemade tube coolers installed near the keel for protection. Many commercial fishing boats before steel hulls became common had tube cooling. Often homemade with copper pipe and some sort of bumper in front of the tubes for protection. 30' of tubes would cool about 300hp in the North Pacific.
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