Air Cooled Inboard?

Discussion in 'DIY Marinizing' started by feetup, Nov 8, 2006.

  1. feetup
    Joined: Oct 2006
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    feetup seeker

    I have a small single cyl. air cooled diesel engine that I can't help thinking would be an ideal power plant for a smaller (25') sailboat. I'm thinking about some form of ductwork for cooling air with a water trap, and adaquate engine room ventilation to exit the hot cooling air. Has anyone tried to use an air cooled engine in an enclosed engine compartment? I'm sure that a water cooled exhaust would not be too difficult but does an air cooled engine work at a higher relative temperature (disregarding exhaust) than the 180 or so degrees of a liquid cooled engine?
  2. Frosty

    Frosty Previous Member

    Yes ---I have, ducting and lots of air from a cool source. Then of course ducting out is just as important if not more so. Wet Exhaust?? I didnt use one as diesels gererally run fairly cool.

    I bought a cheapo car type mechanical temp guage and made a bracket to hold it to the cylinder head. I was delighted to find that at low power (this was a gernerator) the temp was under,-- at full was a tad warm but nothing to worry about.

    I used a car 12v heater or air con blower motor to suck air from the engines cowling which I made. This was 1 meter by 1 meter plastic insulation stuff like what they make 'flip flops' or thongs from ( you know shoes with a plastic strap on) This was i inch thick. I made the edges from 1 inch angle alluminium,-- looks good

    The exhaust has not even discoloured the paint as it exits the head.

    No holes in the boat, no pumps, no seacocks, no sloshing noises, no heat exchangers, no electrolisis, no leaks, and when I put the cat on the beach I use the generator as usuall.

    My air con condenser is also air cooled and enclosed it is combined with the gen cooling system so I can put the air con on also.

    I must buy a digital camera one day!!!!
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    FAST FRED Senior Member

    For more propulsion you might contemplate a reduction gear.
    A pair of V belts should do..

    A really EZ retrofit is a rototiller engine , most have 6-1 reduction ,factory installed.

  4. waikikin
    Joined: Jan 2006
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    waikikin Senior Member

    Feet up, my dad installed an air cooled Lister in a yacht, fantastically reliable & great after a swim or dive as he fitted a door to the duct work for heating, you've gotta make sure of the square inches of duct for the length of duct for the HP so you don't cook it, the guy who bought dads boat knew "better " & replaced the oversize ducting with a little corragated tube & killed it! Regards from Jeff:)
  5. Mikefleetwood
    Joined: Jul 2006
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    Location: Cornwall, UK

    Mikefleetwood Junior Member

    Further to all the above, I'm interested in the idea of water-cooling the exhaust of my Lister (SL1). The boat still has a sea-cock from the original installation (Stuart-Turner, I think). A friend suggested that I could feed water into the exhaust and the pressure would force it out the exit, wit no pumping needed. Currently, the exhaust is through the side and I'm considering re-routing it through the transom. Although I am concerned about the possibilty of water forced in during launch (off the beach). There were two reasons for considering water-cooling:
    1 - keep the exhaust cool, so I can use "plastic" tubing, particularly for the proposed longer run to the transom.
    2 - To reduce the noise, there being no "silencer".

    So, what does the panel think? Am I wasting my time considering water-cooling?
    What do I do to keep sea water out of where it shouldn't be?
    Any other advice?

    PS. the boat's a 16' clinker-built fishing boat of unknown age!
  6. Frosty

    Frosty Previous Member

    Your on the right track. It all depends on how high the injection point is on the manifold and the manifold itself in comparison the the outside water line.

    You also mentioned that you wouldnt use a pump -- do you mean that the sea cock is able to flow water into the manifold without a pump?. If so No No dont do that. It would be better to use a pump as when the pump stops the water stops--IF you use an impellor pump.

    When you stop the engine ( drifting -fishing etc) you do not want water going into the manifold- it will fill up and flood the engine.

    A water cooled exhaust is a simple matter but some very important rules need to be adhered to.

    Some pictures would explain this. Try googling Vetus exhaust, I think they have a page from their fitting manual on this subject.

    Many engines have been destroyed from wrong wet exhausts.
  7. Poida
    Joined: Apr 2006
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    Poida Senior Member

    I would think you would be better off if you could stick with aircooled engines that were designed to be enclosed, Trailed air compressors for example have air blown over them and the fans are incorporated in the engines.

    Engines that are designed to be in the open air and usually have fins on them may not be suitable as they depend on a circulation of air from the bottom. Any attempt to blow air at them may cause hot and cold spots and cause contraction cracks.
  8. Mikefleetwood
    Joined: Jul 2006
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    Mikefleetwood Junior Member

    Hi Jack Frost!
    Thanks for the prompt reply.
    My friend suggested I wouldn't need a pump as there the water would not need to circulate an engine block. The Lister engine is quite tall and sits mostly above the water line. I was going to have a steel downpipe made from the exaust port, with the water injected from the seacock slightly below the waterline. Due to the height of the engine, i don't think there is too much risk of water rising to the manifold when stopped. I was thinking of making the "downpipe" fairly large diameter to act as a reservoir to prevent water in the exhaust being forced up to the manifold.

    I did look at the Vetus site, but need to examine their manual in more detail.

    I will thry to sketch what I have in mind, but this may take a while as I am not sure how to post pictures to this forum.
  9. Frosty

    Frosty Previous Member

    I would have immagined that you you would be close to the water line.

    What you can do is cheat a bit by making the exhaust pipe go upwards first. You would normaly lag this bit. Then when it is up and way above the water line you can inject the water after you turn the pipe down again.

    Another thought is about reversion of the exhaust gasses especially on an engine that was not expected to have water cooled exhaust.

    'Reversion' is gasses actually being sucked back into the engine during its cycle . Engine with expected water cooled exhaust have the correct cam shaft and valve overlap to avoid this.

    Again you can cheat this by injecting further down the pipe.
  10. Mikefleetwood
    Joined: Jul 2006
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    Location: Cornwall, UK

    Mikefleetwood Junior Member

    I think the manifold is about 12" above the waterline, but I haven't measured (the engine is out of the boat as it's being re-built). Making the exhaust go up first sounds like a good idea - I guess some sort of anti-siphon would be useful?

  11. seo
    Joined: Mar 2007
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    Location: Maine

    seo Junior Member

    Back in the '70's engines built by the German firm "Deutz" sold quite a few air-cooled diesels for use in fishing boats. I worked on Deutz powered lobsterboats in Maine, and on Salmon seine skiffs in Southeast Alaska. I've worked on one yacht, about a 30' sailboat, that had a one-cylinder Deutz, and on a couple of sailboats with Lister/Petter air-cooled diesels. I also sailed as engineer on boats that had Lister/Petter air-cooled generators and pumps.
    They work fine. As pointed out in other posts above, there has to be a good supply of air. It's possible to duct only one side, so that the engine is either sucking air out of the engine compartment and blowing it overboard, or sucking cold air in and discharging warm air into the compartment. This was common on the Maine lobsterboats.
    The Deutz engine is very efficient, and they claim that part of the reason is that the cylinder head temperatures are much higher, leading to complete combustion. However, the Deutz gets hot, and will heat a lot of space.

    As far as exhausts go, I don't have an opinion on whether the eductor type injection you propose will work. It doesn't make sense to me, but I could be very wrong. It would be no big deal to get a small Jabsco-type pump to run off a belt and supply water to the wet exhaust. This is necessary on all the water-cooled engines that use keel coolers instead of heat exchangers.
    Another option might be a dry exhaust. I used to have a 28' Herreshof sailboat (H-28) built in 1951, and when I bought it in 1976 it still had its original Universal "Blue Jacket Twin" engine with a dry exhaust. It was just carefully fitted pipe with good heat shield lagging. It worked fine.
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