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Thread: High Thrust Yamaha's

  1. #1
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    Default High Thrust Yamaha's

    I was looking at outboards today and seen that yamaha made a high thrust 8 hp. It's 4 stroke, but it weighs 20 pounds more than the 4 stroke. So what all did they put on it to make it high thrust?

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    the shaft length [ TRANSOM size ] an it could be a 4 blade prop like OMC did on there [ 20" / 24" ] not 15 " like the regular one

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    from looking at the specs it looks like the shaft lengths are both 20". The only difference I could find was that the prop was bigger, and the exhaust comes out behind the prop. So the blades are always supposed to be biting "clean" water. according to specs the stock 4stroke 8 hp weighs 80 lbs, the high thrust weighs 107lbs. I'm not going to get the motor. I was just wondering where all the extra weight was coming from.

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    Lower gearbox is a lot beefier. Basically it has a 15hp lower-unit attached to a 8hp motor. Gear ratio is lower too, almost 3-to-1. Had a HT8 kicker on a 26ft/8,000# boat, and it pushed it to hull-speed of 6 knots. For some reason Yamaha was forced to de-rate their HT9.9 down to 8hp for a few years when their 9.9hp failed to pass some new EPA emissions requirement. They have now tweaked the 9.9 back into compliance, so the HT9.9 is a slightly better kicker. But, if you run across a killer deal on a T8, go for it. But, the HT's are not meant to be used on small dinghies or canoes. The low gearing and low pitched prop will only push whatever boat they're mounted on to slow speed. For small boats you'd be better off with a regular 8/9.9 and really zip across the water.

    Unless, you plan to use your canoe as a tug-boat and pull a raft of logs behind it.

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    Member BluNosDav's Avatar
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    Lightbulb

    After reading more threads about "freighter" canoes carrying 1000's of pounds of cargo,
    maybe a "High Thrust" motor is a good thing?

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    Quote Originally Posted by PugtSounDav View Post
    After reading more threads about "freighter" canoes carrying 1000's of pounds of cargo,
    maybe a "High Thrust" motor is a good thing?
    nope,

    They are the wrong motor to have. These motors are usually found on large boats as a kicker. The shaft length is usually too long. Our rivers are shallow, and is certainly no place for a long shaft kicker motor of the back of a transom that's maybe only 14-19 inches tall. Due to the heavier and larger prop, and bigger gears, they usually weigh more than a comparable short shaft motor. Canoes are highly efficient and use little horsepower to move big loads slowly, but fast sections of current does require as much RPM's as you can get from your motor, not thrust. On the Yukon pushing a moderate load, I still hit bottom occasionally, and in some spots with a 9.8......could only do 7 mph against the current. Had is used a high thrust kicker.....I certainly wouldn't have made it up river.

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