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Thread: Yamaha Genesis 4-cyl engines (RX1)

  1. #1
    New Member AlaskanOutdoorsman's Avatar
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    Yamaha Genesis 4-cyl engines (RX1)

    Looking for individuals who have built an airboat with the 1000 cc Yamaha 3-cyl or 4-cyl engines (snowmobile or motorcycle). I'm in a rebuild and questions regarding gearbox's and/or redrive options. Thanks.

  2. #2
    Level 1 Supporter Bart's Avatar
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    Re: Yamaha Genesis 4-cyl engines (RX1)

    it looks like you have a fun project that you are working on. you might have to reach out to some of the experimental air craft groups. i see that there are a couple of different methods that some of them have used to convert the Yamaha 4 stroke to use a prop.
    about the best one i have found is the link below. from what i see, he has designed an adapter plate, so a rotax type C gearbox can be bolted directly to the motor. and has made a couple of air trikes. the design is very clean looking.
    http://www.trikepilot.com/forum/topic/1091

    your Yamaha power plant looks like a good dependable choice. and after looking at this link and watching his u-tube video, it has got me thinking, this could be a fun option. when i find the right deals on a used Yamaha 4-stroke motor.
    it is just getting the gearing to match the full power band on the motor to the prop.
    where when this motor is on a sled, the clutch is set to engage at 43 to 4400 RPM, and the 140 HP is at 10,500 RPM. the airplane guys, don't like to run the motor over 8500, that leaves 25 HP on the table.
    but from what i have seen from looking at what the gentleman in the link has learned and put together. he defenitly put in his time, and it looks good.
    good luck with your build

  3. #3
    New Member AlaskanOutdoorsman's Avatar
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    Re: Yamaha Genesis 4-cyl engines (RX1)

    Thanks Bart. I've been all over the aviation forums - that's where I came up with the idea for this power plant. You can't beat the cost, weight, or power these put out. There are about 50 aircraft flying with Teal's adapter set-up if I read various forums right; he uses a Rotax C-style 3:1 gearbox. There are many others flying with different adapters and various gearbox's.

    I want to add a turbo charger so I'm not going to go Teal's route. The Rotax Cbox is doing fine at 135hp but it's normally used on a 65HP Rotax engine. I don't want to risk the time, effort or money having it on a system at 200 or 250hp. I've found some options for other adapters/gearbox's but frankly, I think a redrive/belt drive system would be more affordable than the gearbox/adapter route which costs about $3-4K. Problem is designing one when you've never designed one. Could be more costly in the end.

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