Auto engine marinization

Discussion in 'DIY Marinizing' started by Guest, Jun 10, 2002.

  1. FAST FRED
    Joined: Oct 2002
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    Location: Conn in summers , Ortona FL in winter , with big d

    FAST FRED Senior Member

    Should be around .55 BSFC. .55 x 100 / 6.75 (pounds of fuel per gallon) = about 8 gallons per hour.

    THANKS!!! The gas engine mfg. are really close with this info!

    A "good " direct injection diesel would require 5gph , and turboed intercooled and electric injected might get be closer to 4gph.

    But of course the diesel fuel is heavier.


    FAST FRED
     
  2. fasteddy
    Joined: Jul 2006
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    Location: gainesville ga

    fasteddy Junior Member

    I got real tired of hard to program OEM computers. I started researching this almost 20 years ago when I had an Opel 1900 Sportwagen with a Bosch K-Jetronic. It was only about 10 years ago that I finally found the first systems/companies to do this work. I'm stubborn like that. I now sell and install user programmable efi systems for almost any gasoline/alcohol engine, NA or super-/turbo-charged, with or without nitrous. My all time bang for the buck system is a modified Megasquirt2, followed by an SDS. I've never had luck with chip reprogrammers - too many re-do's to get it right. You have to real time tune with proper sensors - egt, wide band O2 sensor, accurate tach, and monitoring of injector duty cycle and fuel pressure. Boats really need some form of integrating accelerometer, since it's hard to put them on a dyno. I acutally prefer to tune cars the same way, as I do not trust the accuracy or repeatability of a wheel dyno, or the real correlation of the results to real world results. Boats tune a LOT different than cars. Unless you have a clutch in there (bet you don't), you MUST have a very low, stable idle, or like to buy outdrives. I tend to think of props as like a torque converter in a car automatic transmission, unfortunately, without a lockup clutch. This analogy fails to match reality as prop rpm increases. I therefore build/tune boat motors with a cam optimized for the customers requested cruise rpm for best overall performance, and I always advise that you buy all the cubic inches you can get to get all the torque you can get on a wide, flat torque curve, to keep the rpms as low as possible. Engine life decreases by the square of the increase in rpms, and even that may be optimistic.
     
  3. Go-Man
    Joined: Aug 2007
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    Go-Man Trusts In Thrust

    car engines in boats

    i'm building a 14' catameran hull, ive seen shallow bottom boats running big blocks, so i figured a way to put in a small corolla type engine (100 HP) and figure cooling,
    (just have a pump pushing water over a regular car radiator), lubricant, exsaust, and fual. as for stress, its just not going to go that fast. but from the engine to the prop i know knothing about.:?:
     
  4. CDK
    Joined: Aug 2007
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    Location: Adriatic sea

    CDK retired engineer

    To get rid of the generated heath you need a water cooled exhaust, which, as far as I know, is not available for a Toyota engine.
     
  5. Corpus Skipper
    Joined: Oct 2003
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    Corpus Skipper Hopeless Boataholic

    You can use a "dry stack" exhaust, liberally wrapped with insulation designed for the purpose. Commercial boats have used this type of system for ages. I don't know about splashing water through a radiator tho. You can get "universal" raw water pumps and heat exchangers and plumb them in, or go for a keel cooler since yours won't be a high speed vessel. Keel coolers are very efficient, and require less maintenance than a heat exchanger. Again, commercial boats have used this system forever.
     
  6. CDK
    Joined: Aug 2007
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    Location: Adriatic sea

    CDK retired engineer

    A dry stack is little more than a theoretical possibility. There is no flexibility, so you'd have to use a chimney or an over the transom exhaust with a heat shield. Both will break off unless the engine is ridigly mounted, so there'll be a lot of noise and vibration.
    The little Toyota engine will generate approx. 70 KW at the flywheel and a little over 200 KW of heat thru the exhaust and the cooling system. No problem in the Corrola it was intended for, but unbearable in a slow moving boat. Commercial vessels may use a dry stack, but have a different displacement to power ratio, diesel engines, lots of space and a crew that has learned to live with the discomfort.
     
  7. Corpus Skipper
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    Corpus Skipper Hopeless Boataholic

    Well, there are some small (25' or less) shrimp boats around here with dry stacks on small 6 banger chevys or something like that. It doesn't seem to be too much of a hinderance. And there are flexible stainless exhaust hoses that go between the manifold(s) and the stack(s). These boats aren't any noisier than one with a wet exhaust. They run the stack through the deck, up the back side of the wheelhouse, and maybe 3 feet above the roof. They use big cylindrical mufflers, maybe 3 feet long, and 6 inches in diameter. Some put a cage around the muffler, some wrap it with insulation blankets. All in all, it's an inexpensive, very functional system, without the worries of wet exhaust.
     
  8. Go-Man
    Joined: Aug 2007
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    Go-Man Trusts In Thrust

    engine to prop

    i said somthing like a corolla (SMALL, its a 14' boat:!: ), i had the exhaust figured, I need help from engine to prop!
     
  9. Go-Man
    Joined: Aug 2007
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    Location: Placerville, CA

    Go-Man Trusts In Thrust

    engine to prop

    i said somthing like a corolla (SMALL, its a 14' boat:!: ), i had the exhaust figured, I need help from engine to prop!
     
  10. marshmat
    Joined: Apr 2005
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    Location: Ontario

    marshmat Senior Member

    A 100 hp Corolla engine, even if you detune it to 60-70 hp for continuous running in the boat, will make any 14-footer I know of go like a bat outta hell.
    From engine to prop is a relatively simple matter compared to sorting out the engine itself. Take the ratio of the engine's cruise RPM to the desired propeller RPM at cruise, and go down to your local rebuilt/used boat parts yard (every port town has at least one such place, unless you're in the heart of an expensive yacht-strewn megacity). Look for a F/N/R reduction gear of something close to that ratio you calculated. Well built gears last pretty close to forever unless they're really heavily abused (run with no oil, or with too big an engine, etc). The shaft seal, or "stuffing box", is a pretty simple component you can probably get from the same parts yard. You might also be able to get the struts, shafts and thrust bearing (if it's not built into the transmission) pretty cheap if you look hard, but wear items like the cutless bearing will need to be bought new. This is of course assuming you're talking about shaft or V drive; an outdrive leg is a different matter.
    A dry stack exhaust should be feasible if you have a convenient place to run the stack. Make sure it has good heat shields around it or you'll be spending an inordinate amount of time in the burn ward of your local medical clinic.
    A car radiator will disintegrate in a matter of weeks in saltwater; a year (two at most) in fresh. If you don't want to cool the engine directly with raw seawater, a heat exchanger of some form is needed- either a keel cooler or a counter-flow saltwater/coolant heat exchanger (probably $900 or so if you buy a dedicated marine model, more like $75 if you're good with bending and welding aluminum or stainless steel and have some time to kill).
     
  11. Corpus Skipper
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    Corpus Skipper Hopeless Boataholic

    Thanks Matt, excellent advice. Basically what I was trying to get across.
     
  12. Go-Man
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    Go-Man Trusts In Thrust

    reply

    im 2 1/2 hours from salt water. its too rough for 14'. anyway i dont think i could
    get it there
     
  13. Go-Man
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    Go-Man Trusts In Thrust

    also thats excactly what i needed, marshmat, Thanks!
     
  14. FAST FRED
    Joined: Oct 2002
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    Location: Conn in summers , Ortona FL in winter , with big d

    FAST FRED Senior Member

    "There is no flexibility, so you'd have to use a chimney or an over the transom exhaust with a heat shield. Both will break off unless the engine is ridigly mounted, so there'll be a lot of noise and vibration."

    Quite flexible SS exhaust couplers are at many sources , even flexible enough for a soft mounted engine if noise is a concern. As diesels have fairly low exhaust gas temps (compared to gas engines) a muffler and external exhaust can be wrapped with a few layers of asbestos or its "modern " replacement. A lagged exhaust blanket can lower the temps to EZ hands on temps , but is about $100 for every 4 ft.

    The usual is to install everything in an insulated box, although if some exhaust is exposed it can warm soup or whatever.

    Dry stack and keel cooling is the cheapest all weather all condition exhaust , although depending on muffler selection may (or not) be the quietest.

    FF
     

  15. marshmat
    Joined: Apr 2005
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    Location: Ontario

    marshmat Senior Member

    Of course, if you're going to do a custom exhaust anyway, you may as well form a round, level section about 12" across into the exhaust pipe, right where it exits the manifold- clamp yer frying pan on here, add a pickerel and some spices, and presto, you don't have to carry a stove anymore! :D
     
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