High Thrust outboard engines

Discussion in 'Outboards' started by rasorinc, May 29, 2014.

  1. rasorinc
    Joined: Nov 2007
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    Location: OREGON

    rasorinc Senior Member

    I am going to buy a 9.9 High Thrust outboard as a kicker engine and to power my 13' fishing boat. They run about $ 600.00 more than a regular engine. My question is what if I bought a 15 hp or even a 20 hp regular engine would the extra hp be equal to the High Thrust engine in powering my boat (s). Would the regular engine be more fuel efficient? Would this answer carry up to a 60hp high thrust vs a 75hp regular engine? I'm not up to speed on outboard engines so all help will be greatly appreciated.
  2. keysdisease
    Joined: Mar 2006
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    Location: South Florida USA

    keysdisease Senior Member

    I owned a pair of Yamaha 9.9 Hi Thrust Yamaha's on a 36ft catamaran. My previous experience with a "regular" outboard would be to put it in gear, open the throttle, then go get a beer while the tiny little propeller spun its little brains out trying to push the boat. About the time I walked back from the cooler and had taken my second refreshing swig the boat would have begun to move.

    With one hi thrust motor, when you put it in gear you had better be holding onto something if you were standing up, because we're moving like right now.

    Hi thrust is not for high speed, it will push large loads with authority and while it will also push a 13ft fishing boat, it may or may not plane it. The main difference is the gearing and the propeller size. If I remember correctly my old engines were spinning 12" props with large area blades (elephant ears) which are enormous by small outboard standards.

  3. PAR
    Joined: Nov 2003
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    Yep, Key has is about right. A typical 9.9 HP will have a 2:1 gear ratio, while the high thrust will be around 2.5:1 and swinging a bigger prop, often with a bigger skeg too. It'll still spin up and get you on plane in a little boat, but it'll take longer then a regularly geared engine of the same size.
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