Weed eater engine conversion

Discussion in 'DIY Marinizing' started by Ward, Jun 2, 2003.

  1. whackeroutboard
    Joined: Aug 2011
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    Location: Knoxville TN

    whackeroutboard New Member

    after many hours of reading this thread over and over i finally got my weedeater converted. Im using a Stihl FS36 weedeater, no gear reduction, spinning a prather 275 prop. I have this outboard mounted on a caddis pontoon fishing float. It pushes me along rather well, im guessing at least 5 mph, maybe around 8. Im happy considering i only have about 75 bucks in the outboard.
     

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  2. ben2go
    Joined: Jul 2008
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    Location: Upstate, South Carolina,USA

    ben2go Boat Builder Wanna Be

  3. Ed-H
    Joined: Mar 2010
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    Location: Montana

    Ed-H Junior Member

    Ooooooooooooooh K!
     
  4. Erich_870
    Joined: Feb 2009
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    Location: Juneau, Alaska

    Erich_870 Junior Member

    Here's a video I put together where I talk about how I built my boat motor.



    Erich
     
  5. NZ Rob
    Joined: Aug 2011
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    Location: New Zealand

    NZ Rob Junior Member

    Work in progress on a 1 hp outboard for a kayak. I'm wanting reliability and hull speed only. This is really only at the "proof of concept" stage with most of the bits and pieces being scrounged. If it works out I will lash out on stainless steel shafts etc

    32cc McCulloch (clutched version) $13.00

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    2.1 gearbox... output shaft at 90 degrees to input. $5.00
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    Suprised? It's so crazy!... but it works!
    Meaty cogs! Whether it lasts is still to be seen... at $5.00 NZD who cares!
    Youngs T-10 prop. $ 24.00 ($16.50 plus shipping/imported from USA)

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    The drive shaft is aluminum tube with the standard square shaft crushed inside with a vice. The end that fits in the drills chuck is an old bit that has been hammered into the tube.

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    I've had this running in a barrel. It seems to be fine, clutch engages and doesn't seem to be slipping. There appears to be easily enough thrust to get me along in the kayak at least as quick as padding.

    I need to sort out the controls/steering and get it out on the water.

    Problems? Oddly enough, the drill's housing is not waterproof... go figure? I shudder to think what salt water will do to it. :D
    (Future problem)

    Other thoughts... these old drills have two ratios 2.1 and 6.1, I have an 8 inch prop that I might give a whirl at 6.1 and see if that generates much thrust at 500 - 700 rpm at the prop.

    Your thoughts?
     
  6. NZ Rob
    Joined: Aug 2011
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    Location: New Zealand

    NZ Rob Junior Member

    Last edited: Sep 14, 2011
  7. pistnbroke
    Joined: Jan 2009
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    Location: Noosa.Australia where god kissed the earth.

    pistnbroke I try

    Good idea on the white plastic domestic waste pipe..various sizes and can be obtained and it will push out quite a way when heated......I have a 100cc british seagull with a 4 :1 gearbox ..its only 1.5 hp but drives a 10 inch prop ...the more you gear down the lower your max speed but the greater the bollard pull ..

    Nice job
     
  8. NZ Rob
    Joined: Aug 2011
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    Location: New Zealand

    NZ Rob Junior Member

    Hi pistnbroke,

    My workshop isn't very extensive (just handtools) and a smallish budget limits me to cheap easily worked materials.

    I do plan to take this into the ocean, where there is a reasonable chance that my kayak will go turtle and drown the engine, cheap easily replaced solutions work for me.

    Thats really the whole reason that I'm going down the weedeater outboard path. I could buy a 2 hp yamaha or Seagull and bolt it on to my kayak and have a more powerful and reliable outboard than I could ever make, but it will get wet and I can't afford to replace it that often. Once I have the shaft/gearbox/prop sorted I can easily replace the engine itself, if it fails.

    I'm inclined to tinker with this sort of thing anyway, it gives me something to do when I'm not fishing... more tinkering than fishing at the moment. :)

    I have that 8 inch prop that I mentioned earlier attached to a second weedeater but at 2.5 to 1 it bogs down (no suprise there) and at 6 to 1 it appears to give less thrust than the T-10 prop, so I'm going with the original setup at this point.

    Regards
    Rob
     
  9. NZ Rob
    Joined: Aug 2011
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    Location: New Zealand

    NZ Rob Junior Member

    Ok... the old tank leaked when it was pulled from the water and placed on the kayak. I've bought and installed a new 1 litre fuel tank, designed for a 50cc pit bike, hopefully the new seals will help stop fuel leaks as it is orientated to have the cap on top when the engine is running,

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    I've installed a fibreglass rod through the weedeater housing. It allows me to clip on and steer the outboard with my feet, using existing rudder controls. Once I work out the optimum place to have the clips, I can shorten the rod down a bit. That is 10mm fibreglass rod... the galvanised clips are used to hold electric fences on to that type of rod.

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    I've put a handle on the top of the weedeater to make it easier to tilt it from the kayak's seat (2 person kayak).

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    It's all looking good so far... I've had this running in the barrel for quite a while and it doesn't seem to overheat either the engine or the clutch. I just need an afternoon pass from Wee Wifey, so I can get out to a quiet river to give this thing a whirl and confirm this in real conditions.

    The weather is not so good today so I might wait for next weekend, weather permitting.

    Another youtube video http://www.youtube.com/watch?v=JpE7Q7knCf8
     
    Last edited: Sep 25, 2011
  10. NZ Rob
    Joined: Aug 2011
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    Location: New Zealand

    NZ Rob Junior Member

    Got out to the local river on the weekend... too shallow, too swift and too narrow... however, the weedeater outboard prevailed and performed well enough for it's first real outing.

    http://www.youtube.com/watch?v=1pVpLyHrpgA

    :)
     
  11. Erich_870
    Joined: Feb 2009
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    Location: Juneau, Alaska

    Erich_870 Junior Member

    Great video! It looks like your steering setup works well! Can't wait to see what the top speed is when you have a chance to open it up!

    Erich
     
  12. rmenasco
    Joined: May 2010
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    Location: Florida

    rmenasco Junior Member

    Finished the new hybrid a little late for early teal, but it will be ready for the regular season.

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  13. Erich_870
    Joined: Feb 2009
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    Location: Juneau, Alaska

    Erich_870 Junior Member

    Very nice! Can't wait to see a pile of ducks on it.

    What's the cap for at the top of the shaft tube, right below the motor?

    Erich
     
  14. rmenasco
    Joined: May 2010
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    Location: Florida

    rmenasco Junior Member

    The cap is to fill the transmission fluid. It also houses the location for the shaft lock, so that the shaft can be removed at anytime.
     

  15. NZ Rob
    Joined: Aug 2011
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    Location: New Zealand

    NZ Rob Junior Member

    Nice boat... how much water do you need for it?

    What brand, cc, horse power is your engine?
     
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