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Thread: Mini with a Rotax

  1. #1

    Mini with a Rotax

    Hey! I'm brand new to this web-site, I'm really liking it! I have a mini with a 583 Rotax on it that goes like crazy! It started with an idea that turned into a bunch of ideas that all formed themselves into a boat! Lets see if these pics work.

  2. #2

    Re: Mini with a Rotax

    Here is another pic...

  3. #3
    Administrator Papee's Avatar
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    Re: Mini with a Rotax

    Thanks for joining our forum, I've seen your boat before and it is a great looking setup. We all know that everyone likes to see photos. Feel free to add information about your boat anywhere it fits. The more information we have about the minis the more it will attract new users to this forum. It's nice to talk to others with the same ideas without confusing the idea of a mini airboat with the full sized boats. I think it just makes it easier for the new person getting into airboating and minis specifically to find the information needed to purchase or put together their first airboat.
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  4. #4
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    Re: Mini with a Rotax

    I see that your runing a 3 blade warp drive. What length is it, and roughly how much pitch are you running? Which gear box & gear ratio are you using? I'm very curious because I'm seriously considering the 583 motor for my mini. I am currently running a 503 DCDI Rotax with a C-Box 3.47-1 gear. I'm using a 70" 3 Blade warp dive prop. My boat runs dry, but not as well as I'd like. I need a bigger and better power-2-weight option.

    It's good to see another Roatx mini on the site!
    Chad

    Live life on the edge! It's less crowded and there's a much better view....

  5. #5

    Re: Mini with a Rotax

    I love my rotax! Its great! The 583 runs about 85 hp at higher elevations and more at lower elevations. The prop is a 66" prop and set at only 9 degrees right now. It goes where I want it to, even loaded down. I was thinking I had about 600 lbs in it the other day, but that was just guys, 1 @ 265, 1 @ 200, and another @ 160 plus our gear and half throttle was more than enough to get us all out and back in. I would suggest finding a stock snowmobile motor. I have an A drive Gear Box, I believe and its 2.58:1 I run it at 7k rpms so that would about give me the best rpms for my prop. Any suggestions or anything else, let me know. I'm up for learning whatever I can!

  6. #6

    Re: Mini with a Rotax

    I think the 583 takes a B gearbox - I don't even know if they make the A box anymore.

  7. #7
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    Re: Mini with a Rotax

    Yeah Prob a B-Box. I had a 2.58-1 B-Bow on my 503 DCSI. Glad to move up to a bigger gear and electronic ignition. Now it's time for more HP. You guys running the clutch or direct gears? I'll never go back to gear on gear / no clutch again. So much smoother at idle with the clutch. No low rpm idle, rattle your teeth out vibration when using a clutch.
    Chad

    Live life on the edge! It's less crowded and there's a much better view....

  8. #8

    Re: Mini with a Rotax

    It must be the B box then... Yeah, its gear to gear and it doesn't rattle or idle at low rpms. I would rather get the idle down even lower than it is. It idles at 2k rpms now. The other day the rope on the pull start broke and kept breaking. I was at the launch and really wanted to go out hunting... My bro, Utah Scooter, and I pulled the pull start off and wrapped some baling twine around the pulley. We had to wrap it, pull it, wrap it, pull it, and so on. It didn't take too long and we had it up and going! As soon as it warms up, the prop can just be spun and it'll start. So wasn't too worried as we went out hunting. We sat out there for a little while and when we went back to get the boat, I just grabbed the prop and spun it twice and it fired right up. I'm impressed with that motor!

  9. #9
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    Re: Mini with a Rotax

    Yep, I know what you mean. I've been there and done that several times before. That's the only downfall to having a clutch. Hand cranking via the prop is no longer possible. The purpose of the clutch is to disengage the prop from the engine allowing it to start and operate at idle without vibration. When the engine is idling (below 2350 RPM) the prop is not turning. Installation of the clutch replaces the gear box flywheel and the hardy disk.
    Added weight is approx. 3 Lbs. At this time the clutch is only available in the "C" gearbox.

    The clutch is made much like a go-cart clutch, just a larger scale version. As the crank turns, the spring stretches thus expanding the magnets away from the center of rotation (the crankshaft). At which time the magnets are magnetized to the outer drum and the prop starts to spin. As the engine slows below the 2350 rpm mark, the spring contracts and pulls the magnets away from the drum, thus releasing it and allowing it to free spin.


    I found this description and photo for the rotax clutch on a retailer's website:

    No one will ever dispute the fact that a 2 cycle engine is not happy at very low RPM's with a large flywheel attached to its PTO end. The flywheel of course is the propeller. This dissatisfaction is usually responded to with severe shaking and rough running. This action can be easily proven by simply removing your propeller from your gearbox and then start your engine. You will notice that it hums like a sewing machine (kinda), well at least it's no longer trying to shake it's self off of the motor mount. The reason for this smoothness is due to the fact that the engine is not laboring to spin your propeller at idle RPM. Even with the propeller installed, the engine eventually will smooth out at around 2800 RPM.
    Chad

    Live life on the edge! It's less crowded and there's a much better view....

  10. #10

    Re: Mini with a Rotax

    Thanks for the info on the clutch Spyda. That would be something to look into. As for now, I'm happy with the motor I have, its very reliable and I couldn't be happier. Mine doesn't idle so bad, it doesn't rattle at all. I have a square of a mud flapoff a semi truck under the whole motor to absorb some of the vibration. It works great. I even have some under the motor stand where it bolts onto my boat. Is the idle supposed to be around 2k rpms? I'm scared to drive the boat onto my trailer because of that, it idles pretty fast so it goes fast onto my trailer. Faster than I'm comfortable with! Ha Any and all info about this motor is appreciated. All I know is that I'm very impressed, its low maintenance (so far, ha), and its got enough power for me and all I wanna carry.

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