engines: size and efficiency

Discussion in 'Propulsion' started by DaveB, Jul 23, 2005.

  1. DaveB
    Joined: Dec 2003
    Posts: 129
    Likes: 1, Points: 0, Legacy Rep: 11
    Location: Canada

    DaveB Senior Member

    Hi folks,

    I've got a friend who's in the market for a new boat... a 25-28' cuddy which will have a fairly large i/o... some dealers are trying to talk him into a larger engine and I'm not sure about the trade offs. My impression is that a larger engine would:
    -provide more power -> more speed and acceleration
    -be less loaded at a given power output, and possibly last longer (i/o's are based on car blocks... as cars typically operate at less than 2000 rpm this might be significant)
    -consume more fuel for a given power output.

    Are these generalizations reasonable?
    (I appreciate that there are likely exceptions)

    Thanks for reading,

    Dave
     
  2. KCook
    Joined: Jan 2003
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    Location: Arizona

    KCook Senior Member

    I don't have any data to pin this down. But as for "consume more fuel for a given power output" - I think that was a concern from carburetor days. With fuel injection I wouldn't expect much difference. Stronger motor makes more sense (up to a point). Bigger question is when you opt for twin engines as the means to greater total power. Twins will burn more fuel.

    Kelly Cook
     
  3. Corpus Skipper
    Joined: Oct 2003
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    Location: Corpus Christi TX

    Corpus Skipper Hopeless Boataholic

    Always go for the larger engine. It won't have to work as hard, therfore will last longer, and as far as fuel burn goes, horsepower is horsepower. A 4 banger running wide open will consume as much fuel as a big block loping along at 2500 RPM. KCook is right also, twins will burn more fuel even if the total HP is the same due to drag from the drives and increased weight.
     

  4. stevel
    Joined: Aug 2004
    Posts: 118
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    Location: Ventura, CA

    stevel Lost at sea

    I've never heard a powerboater complain about too much power :D
     
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