Marinizing Rotary engine

Discussion in 'DIY Marinizing' started by greendeane, Aug 13, 2008.

  1. powerabout
    Joined: Nov 2007
    Posts: 2,913
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    Location: Melbourne/Singapore/Italy

    powerabout Senior Member

    Hi 351W
    Love to see some photos of your set up?
    Would it pass USCG inspection or was that not your intention when you did it?
  2. 351EFI
    Joined: Dec 2011
    Posts: 7
    Likes: 2, Points: 0, Legacy Rep: 27
    Location: Gibsons, BC Canada

    351EFI Junior Member

    I really don't care about the USCG as I live in Canada. Our Ministry of Transport regulations are similar to those in the US, perhaps even more stringent in some areas. These rules govern standards for new construction, so technically at least, a boat owner can do whatever he likes to his own boat. Having said that, most, if not all of these rules are in place for good reason. The underlying principal is that all components and systems should be fail safe. I'm not stupid, or suicidal. Nor do I want any issues with my insurance company should I have a claim of any sort in which their lawyers could try shift blame over to me for something I've done in the conversion. I've studied our regulations and there is not a lot that refers specifically to EFI, but as far as I can tell, I am in full compliance.

    Do you have any specific questions or particular areas of interest as far as photos are concerned?
  3. mark latham
    Joined: Aug 2014
    Posts: 1
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    Location: Puget Sound

    mark latham New Member

    Mazda Rotary

    I know I'm years late on this thread, but ...

    Would like to see some pictures of the Columbia River Chris Craft 13B engine installation (@ pbjosh). I'm running a 12A in a Hovercraft America HA-5, achieve 'flight' at about 3K rpm, quick cruise at 5K, max power for my app is at 5800 rpm, the design limit on the fan with a 44/90 reduction. She sips about 2.5 gallons/hour at 5K, which is what in a car? Maybe 24 mpg.

    The Christ Craft installation won't go above 3500 rpm because of the torque curve of the rotaries, they really kick in above 5K rpm. So your props and gear reduction are eating up all they have too early. On my installation the fan eats everything the engine has just at its design max, 5800rpm. But there is a steep power consumption curve as the fan spools up to speed, it could be that the props do much the same.

    I signed up because of this thread. I'm looking at replacing the exhaust system, want to move to stainless, the corrosion (because it has been operated in a marine environment, Puget Sound) is truly scary. My mazda mechanic runs a racing shop, not marine. I say this to indicate that he doesn't especially understand why I am antsy about an unprotected exhaust system in a fiberglass craft. But mazda rotary exhausts run HOT, pushing 1800 degrees easily. And I don't have excess water for a water-cooled jacket, my only option is to glass wrap.

    So if I can get a peak at the Chris Craft it will give me hints on other, successful, installations. Will even trade rides if agreeable.

  4. black_sails
    Joined: May 2016
    Posts: 33
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    Location: Minnesota

    black_sails Junior Member

    To original poster and your eight year old post... i'd think a rotary would make a great 'outboard' if you could convert some existing high hp outboard lower to use it, or some super-compact sterndrive if space were a serious concern. Just thinking about it has me start dreaming about miniboats or some kind of DIY super personal watercraft, hmm...

    You're correct about the aircraft use - the rotaries have the advantage of few failure modes. I'm told if they run out of coolant, they will often keep running long enough to get you to land. I'm told if they run out of oil, they will often keep running long enough to get you to land. They may never run AGAIN but the bearing surfaces are small enough and due to different metals expanding at different rates they don't seem to seize. The only thing that seems at risk of occuring is blowing the seals. (hmm, this may have a different meaning among the oceanic going crowd <_< >_>) Even if that happens they apparently just lose half their power but will keep running to get you home - potentially a boon if you have a single engine craft and you decide getting home is less risky than floating waiting for help in the water.

    Downside is what others brought up with fuel efficiency (and emissions) especially at lighter loads, the cars get sorta poor mileage for the power level even driven lightly.

    You might even use the factory transmission (as others have talked of using automatics or manuals) to get the rpm's down to a manageable level without having to do anything custom. In airplanes they often leave it stuck in 2nd i'm told, the transmission is apparently pretty light for what it is and already made to fit to where a custom one gear only box isn't worth making.

    I'd love to see some pictures of installs from any of the people who have commented on the thread if they ever check it again.

    Sorry if everyone wonders why I keep contributing to years old threads. :) I'm a gearhead and I hope some tidbit I know is useful to someone at some point. Engines and such I often know something interesting about - not really hulls or props or boaty stuff.
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