Getting extra torque from your boat motor.

Discussion in 'DIY Marinizing' started by tom kane, Jul 19, 2016.

  1. PAR
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    PAR Yacht Designer/Builder

    Smoking while fueling is actually pretty safe. I've won quite a few 20 dollar bills, betting people that I could drop a lit cigarette into a bucket full of gas, with no ill concerns. This said, Fred is correct, you can't engineer or legislate out stupidity.
     
  2. tom kane
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    tom kane Senior Member

    getting extra torque from your boat motor

    Image shows an early outside view of a Twin choke Weber carb and fuel pump fitted to a boat, with the fuel being fed along under the rub rail from an outboard fuel tank in an outboard well which is isolated from the inside of the hull and drained outboard.
    The fuel pump and carb are isolated from the inside of the hull and vented and drained outboard.
    A very cheap and efficient arrangement and much safer than having any parts of a boat fuel system inside the hull.

    The benefit of using a long induction tube was easier starting because of better cylinder charging, and reliable choke.
    Better and reliable idle setting speed. Could tick over like a slow steam engine speed if required, with a performance motor.
    Instant acceleration because of better charging of cylinders and a lot of other advantages including better power and running at all throttle settings.
     

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  3. PAR
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    PAR Yacht Designer/Builder

    This is in direct opposition to testing and the facts Tom. The longer the intake runner, the harder to start an engine. The length of the runner has little bearing on how efficiently you can enrichen a mixture setting, for a cold start situation. Additionally, the long, cold runner will require a more effective choke and possibly an intake runner warmer. In fact, if you look at the 35 HP type 1 you initially posted as an example, you'll note a separate tube, below the intake "handlebar". This is a tube, taken directly from the exhaust, to warm the intake runner for cold weather operation. Every single port type 1 VW engine employed this strategy, until the dual carb, dual port setup was invented, The single carb, dual port engine also needed an intake runner warmer.. The dual carb, dual port setup with it's few inches long runners, didn't need this contrivance. The same is true on the cross ram style of intakes, where an electric heater or exhaust bypass was employed, to warm the runners.

    As to better acceleration, well another misnomer. The longer the air/fuel charge takes to get to the cylinder, the more you lose throttle response. It's this very reason every single racer, tries their best to make as short and as straight, a set of runners as practical. Engine manufacture have been slow to catch up, but in recent decades have wholeheartedly jumped on what the racers and tuners have developed for years. There's not a single long runner induction system out there, on boats or automotive applications. Look at the intakes used and compared the ones that flow better, they all have the same things in common, straighter runners, shorter runners, except in extremely high output applications (tunnel rams, etc.). Even the tunnel ram, the hallmark of muscle bound muscle cars. The runners aren't any longer than a traditional low rise intake, it's just they don't snake around on top of the engine, but rather stand straight up over their respective intake port, so the fuel can literally fall directly into it from above.

    This said, they have progressively made longer, denser infeed air passages, but this is an altogether different animal and simple physics, to bring a colder fresh air charge to the induction setup. There's no free rides. It's a balancing act and the good ones match everything up in terms of volume and flow. It's just like a boat - increase resistance with a longer runner and guess what happens to the flow. You can cheat to a degree with passage shapes, attempting to hold up velocity as long as possible, but the modest torque gains, are offset with sluggish throttle response, air/fuel vapor dropout and other ill begotten gains.

    [​IMG]

    This is a type 1 VW at the end of its development. Note the very short runners, dumping the air/fuel charge into the head. Compare this to the previous image, where the charge has to travel 5 times as far and tell me which will do better. This isn't a stock engine, but a stock engine was available like this (Solex instead of Webers) and it produced twice the HP of the handlebar style of intake with the same cam dynamics.
     
  4. FAST FRED
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    FAST FRED Senior Member

    "an outboard well which is isolated from the inside of the hull and drained outboard."


    Any tiny fuel sheen on the water may cost thousands in fines from the purity police.
     
  5. mydauphin
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    mydauphin Senior Member

    Little secret..... Carry a bottle of Dawn dish washing soap. When you see the sheen squirt a little... It is amazing to watch it disappear.
     
  6. mydauphin
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    mydauphin Senior Member


    I have seen more than a couple of boat explosions. The sources were bad hoses, trap fuel vapor in engine compartments and a backfire out carb, and people carrying extra fuel in plastic containers.

    I almost had a bad situation on board. I was welding (yes on board, yes dumb idea) and a spark fell on a random piece of styrofoam, that fell on a cushion, that was over fuel tank. A wet towel did the trick.
     
  7. gonzo
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    gonzo Senior Member

    Short runners give an engine a quicker response. That is the reason motorcycles have the carburetors mounted right next to the head. If they have fuel injection, the runner is really short too.
     
  8. PAR
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    PAR Yacht Designer/Builder

    None of these things are the result of bad practices by the regulators or manufacturers. In spite of the best intentions, some will no brain themselves into a hole anyway.
     
  9. bruceb
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    bruceb Senior Member

    Bang?

    Wouldn't a long gas vapor filled tube make a pretty good bomb in case of a backfire?
    B
     
  10. tom kane
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    tom kane Senior Member

    Solving all of your fuel worry problems in your boat in one simple, cheap, efficient method must be a good way to go, it most certainly worked for me. Genius some say.

    If anyone else can not make it work for them they simply have not got the technical and practical knowledge and vision to understand how to make things work or how thing do work. Getting mechanical facts is not easy.
    There is a lot of incorrect assumptions in the previous posts and little point in trying to change others attitudes and ideas about something different and unfamiliar.
    As I said you do not HAVE to have long intake runners (or anything else suggested) but use standard set up but apply the principle of the idea which is to isolate all of the fuel components for possibly creating explosive fumes, and leave your worries behind.
    You do not have to copy my idea but use your own experience to create something better than what exists now. You may even make your fortune and learn something along the way.
     
  11. tom kane
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    tom kane Senior Member

    getting extra

    No.. it does not back fire the long tube suppresses and chokes back fire.
    Try as we might we could not induce a back fire.
    If a possible back fire worries you, a back fire one way valve can be used and this was also tried with no issues about performance.
    A back fire would be more serious in conventional carburetor fitted on a motor
    inside the hull of a boat, flames and fuel would go every where even with flame arrestor fitted.
    With a remote carb fitted provisions can be made to cope with such an occurrence.
    You can still use the principle employed with conventional short induction tubes and EFI fuel systems.
    You do not have to use a induction tube as long as the one shown
     
  12. keith_2500hd
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    keith_2500hd Junior Member

    fast fred brought up henri ricardo, part of his research was variable intake tract. make engine think intake is longer, yet be shorter. 1 setup was simple bicycle tube inside intake, manifold vacuum would pull in reducing interior volume and accelerate velocity. as throttle opened , instant reaction by tube. slide valve carb and variable venture carbs were a solution due to insufficient material when in contact with gasoline. the question about storage of gasoline in different areas was waste of time. the potential of a breeze could carry-over into vessel and interaction with ignition source. the potential for Allison or collision became higher probability for ignition. if a boat is moving forward and gas tank is hung off stern, the displacement of air will roll back in picking up gas fumes and deposit them inside vessel hull. that is why you don't see it.
     
  13. FAST FRED
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    FAST FRED Senior Member

    "if a boat is moving forward and gas tank is hung off stern, the displacement of air will roll back in picking up gas fumes and deposit them inside vessel hull. that is why you don't see it."

    AKA, the station wagon effect.
     
  14. mydauphin
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    mydauphin Senior Member

    Just everyone get a diesel. Frankly, only gas engine boat I would have would be small outboard.
     

  15. tom kane
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    tom kane Senior Member

    getting extra torque from your boat motor

    In this modern World you should spend some time each day trying to understand and believe the impossible.
     
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