Powering a slippery cat with 20 hp. Fuel injected or carb.

Discussion in 'Outboards' started by Russell Brown, Feb 15, 2020.

  1. Mr Efficiency
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    Mr Efficiency Senior Member

    Obviously marine engines are designed for continuous high RPM, there is not much loafing with boats, as the fact they don't have brakes, attests !
     
  2. fallguy
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    fallguy Senior Member

    Of course, but...

    Take two engines of the same design (or similar) and run one at 5000 and one at 5500.

    In the simplest of views; the lower rpm engine is operating about 10% less. I had a 25hp merc and a 30hp Johnson. The Merc and Johnson had similar speeds, but the bigger engine ran at low rs and was quieter and I liked it much better overall. The Merc really ran hard and loud. While rpms were not a factor in recent decision making; if I sit next to a tiller; louder is less pleasant.

    call me silly if need be
     
  3. Mr Efficiency
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    Mr Efficiency Senior Member

    I wouldn't call you silly at all, but there is a band between say 3500-4500 RPM where outboards are quite happy to run without any worry that they are being over-operated. Full throttle is another matter, you certainly risk increasing engine wear doing that, not to mention use more fuel per mile. The noise factor might be as much a matter of how good the cowl insulation is.
     
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  4. Russell Brown
    Joined: Jul 2012
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    Russell Brown Junior Member

    I've been looking again at the Suzuki. Thinking that it may be worth building the fairing around the giant power tilt mount just to see if I can save some fuel. The remote 20 hp only comes with power tilt, but it's the only 20 that seems to burn significantly less fuel than the older carb 20's.
     
  5. brendan gardam
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    brendan gardam Junior Member

    hi russell, i would love to see some pics of your cat if you have any. why are you fitting 1 engine. cats and twins usually go together. i am not critisizing, just curious.
     
  6. Russell Brown
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    Russell Brown Junior Member

    Single engine because that's the way to save fuel, especially when the boat only needs 20 hp, plus the hulls are tiny, so nowhere to put a motor. The boat looks a lot like Grasshopper. Have you seen photos of that?
     
  7. brendan gardam
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    brendan gardam Junior Member

    thanks . i will look up the grasshopper
     
  8. brendan gardam
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    brendan gardam Junior Member

    had a look at the grasshopper video. .looks great . super efficient,
     
  9. Russell Brown
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    Russell Brown Junior Member

    I'm leaning heavily towards buying the Suzuki 20, even though it has the power tilt bracket issue I mentioned above. I couldn't find a pre EFI Yamaha 20 and I'm ready for the motor soon. It's a fairly good deal for the remote Suzuki as it comes with the control box for about $3500 if you buy from the mail-order Suzuki place. My friend got one and it arrived up in 2 days. He had a cooling issue which he sorted out and it seems good. Anyone have anything to say before I pull the trigger?
     

  10. brendan gardam
    Joined: Feb 2020
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    brendan gardam Junior Member

    i see parsons 20hp longshaft advertised on ebay.. neat looking motor 4 stroke . efi. manual tilt. comes with forward controls. i have no idea what the quality is like though.
    i think they are yamaha copys.
     
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