Yamaha High Thrust

Discussion in 'Outboards' started by dskira, Jun 22, 2008.

  1. dskira

    dskira Previous Member

    Good evening Ladies and Gentlemen
    Is somebody has experience with the Yamaha 9,9 Hp High Thrust?
    I see in the specs, it is heavier that the Tohatsu, but the rpm are the same and the gear ration seams also the same. The available prop seams to be of higher diameter than the typical Tohatsu prop.
    Is this engine realy high thrust or it is just a sales pitch?
    I will be glad to hear from you.
    I am investigating to put this kind of HB in a very narrow sailing hull, (Lwl 20'9" Bwl 4'7") and the engine will be only for harbors maneuvering. The displacement will be 2.8 L.T.
    This high thrust motor, if real, will be a nice feature. Cheap, easy to install and easy to service.
     
  2. marshmat
    Joined: Apr 2005
    Posts: 4,127
    Likes: 148, Points: 63, Legacy Rep: 2043
    Location: Ontario

    marshmat Senior Member

    Hi dskira,

    The power output of all 9.9hp outboards is roughly the same- 9.9 hp, give or take a hair, at full throttle.

    The "high thrust" units, and Yamaha is not the only maker doing this, still produce only 9.9 hp. What's different is that they are tuned to produce higher torque at lower RPM. Some do this by modifying an otherwise normal 9.9, others by using the block of a larger engine and de-tuning it to produce only 9.9 hp. Then, they give you a larger gearcase so that you can swing a larger diameter, shallower pitch prop. Thus you get more thrust at lower boat speed. Ideal for heavy, slow boats. But put one on a runabout and you'll be relatively disappointed.
     
  3. alan white
    Joined: Mar 2007
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    Location: maine

    alan white Senior Member

    An expensive motor to put on a small boat like yours. Maybe your displacement (the true variable in choosing an outboard size) is quite low. But maybe your boat is a plank-on-edge cutter of 7000 lbs.
    If under 2000 lbs, a 2-3 hp outboard is big enough. At 2000-4000 lbs, 5-7 hp will do. Buy the 9.9 if you're over 4000 lbs.
    A five horse is maybe 50 lbs lighter on the stern, something to think about.
    That Yamaha has a bottom end like a 20 hp.

    Alan
     
  4. dskira

    dskira Previous Member

    Thank you for your very knoweldgeble answer.
    Yes it is a plank on edge of 3.5 L.T., 7840 Lbs (I made a mistake about the displacement in my previous message)
    It help me to choose the rignt outboard. Thanks again.
     
  5. alan white
    Joined: Mar 2007
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    Location: maine

    alan white Senior Member

    The Yamaha 9.9 would be my choice then. Where in Maine, dskira?

    A.
     
  6. dskira

    dskira Previous Member

    Alan I agree.
    I am located in Rockport, and you?
    I wish all a great day, here it's sunny and will be warm in a while!
    Daniel
     
  7. alan white
    Joined: Mar 2007
    Posts: 3,731
    Likes: 121, Points: 0, Legacy Rep: 1404
    Location: maine

    alan white Senior Member

    Eddington, near Bangor. Last time I was down that way was recently when I was checking out the progress of a new Blue Moon at Atlantic Challenge.

    A.
     

  8. dskira

    dskira Previous Member

    Shame on me, I live very close by and didn't come for now a very long time. I had a good friend as a head, but he left to pursue other interrest.
    I use to go to your direction every other week-end to vist my daughter at Orono University. Now after graduation six years ago, she also pursue other interrest in Spain!!
    I better to be nice to my wife before she also pursue other interrest!;)
     
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