Weed eater engine conversion

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

  1. bgtreefrogs
    Joined: Jan 2008
    Posts: 1
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    Location: Springfield, MO

    bgtreefrogs New Member

    Scooter Motor Conversion

    After years of researching I’m going to take the plunge and build one of these for my kayak. THANKS FOR ALL THE EXCELLENT POSTS! This is the best resource on the web. After reading the posts on the engine sizes I decided on a scooter motor as opposed to an actual Weedeater. The cc’s are larger and they are cheep. It looks like I can also get one with a heavy duty clutch and reduction gear (scooter transmission), also an electric start. I was curious about ripped off’s comments about removing the clutch – it seems that this may not be required if the clutch was actually designed for heavy duty use. You can also get some that have double bearings and three shoes rather than two. Also, the reduction gear might eliminate the need to remove the clutch, since the engine will not be too stressed from the start. I’m going to follow ripped off’s design, which seems bullet proof. Outstanding Design! Any comments? I understand the scooter transmission is a 5:1 reduction. I know this is more than the 2:1 and 3:1 that has been discussed here, but it is already built. Would be great if I could use it rather than use some pulleys and gears.
     
  2. crokseti
    Joined: Feb 2008
    Posts: 4
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    Location: gainesville ga.

    crokseti New Member

    I, m working on a project myself and am trying to adapt a Ryobi 31cc motor with a homemade3 bearing shaft conected to a edger gearbox to which a small prop is affixed.
    I'll purchase a Sears gearbox with 1-to-1 ratio unless anyone here can direct me to another brand that has 2-to-1 gearing.
    Sears-Poulan is around 30 bucks.
    I hav'nt found any info on the ratios of any edger gearboxes.
    I went to Sears and turned one by hand and verified 1-to-1.
    Any help would be appreciated as this project will be done regardless but I don't have much cash to work with.
    I will get the prop from Young's.
    Thanks,
     
  3. evlfkrjohn
    Joined: Feb 2008
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    Location: Slidell, La

    evlfkrjohn New Member

  4. master fisher
    Joined: Feb 2008
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    Location: chelan washington 98816 511 E wapato ave

    master fisher New Member

    attn ripped off

    how did u make the weed eater motor please explain if u have time please email me at maddogmd2005@hotmail.com
     
  5. master fisher
    Joined: Feb 2008
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    Location: chelan washington 98816 511 E wapato ave

    master fisher New Member

    ward





    take a pipe and run it from the muffler and run it into the water it is much quieter
     
  6. SSNgineer
    Joined: Feb 2008
    Posts: 2
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    Location: Port Orchard, WA

    SSNgineer New Member

    Gearbox idea

    Hello everyone. I've been watching this thread for a couple years and I finally have something to contribute. I've been working on a gear drive design based on a 4-1/2" angle grinder head. The gears are made for higher RPMs than a trimmer engine but may not hold up under the higher torque. I haven't done the stress calculations yet. The grinder I bought at Lowe's was $30 and has a 3.08:1 ratio. I am turning an adapter on my mini-lathe that I designed this weekend. I'll try to post some pics soon.

    I'm also creating a solid model in Solidworks for a new housing for these gears. It would look better, but I'm not sure how much it would help for reducing drag or cavitation. I plan on using a Weedless Wedge 2 prop that I found on closeout at Walmart and either my 30cc Ryobi (Homelite engine) or Stihl FS46 for power. Using the formula from Minn Kota's FAQ section, I calculate about 8 MPH at 7000 engine RPM (2270 at the prop) assuming 15% slip.

    Has anyone tried the grinder gearbox idea before? What do you all think???
     
  7. evlfkrjohn
    Joined: Feb 2008
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    Location: Slidell, La

    evlfkrjohn New Member

    Hey guys, sorry for the slow responce but my computer has been down for a couple of weeks and i've finally got it back up! The design isn't mine, I got the plans from livetofly57 on ebay. The plans came with all the info on how and where to get all the parts needed to do the conversion. It is a very nice design and was very well thought out! My nephew is welding up an aluminum foot for me in the same design as a 40lb motor-guide trolling motor to make another conversion. I will contact the seller about posting the conversion again, I would do it myself but I assured him that I would not expose his idea to everyone. But I can say this much, it has a 4:1 gear ratio that is awesome!
     
  8. evlfkrjohn
    Joined: Feb 2008
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    Location: Slidell, La

    evlfkrjohn New Member

    I've never thought about using a grinder gear box before, but it may work well! I guess you won't know until you try! Good luck and keep everyone posted!
     
  9. Guest625101138

    Guest625101138 Previous Member

    The attached pictures shows internal of a small grinder box after 20 hours use swinging an 8" prop. It was pedal powered with speed steup up to the prop so would be better in the other direction. The prop shaft was connected to the tiny pinion. I was surprised that it held up for a reasonable period.

    It was very easy to replace the armature with an 8mm aluminium shaft and use the plastic case for shaft support. The removal took about 1 hour.

    Rick W.
     

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  10. John O`Neal
    Joined: Sep 2007
    Posts: 85
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    Location: Lenexa Ks.

    John O`Neal Junior Member

    Scooter motors are available in larger cc and hp ratings . The Chinese versions can often be purchased for around $150.00 with electric start and a 76mm clutch. I have seen transmissions offered in a 3 to 1 ratio. Try a Google search for motorized bicycle, scooter parts ,mini bikes, you will find an abundance usable parts. A simple method to the bulletproof design that Turn4fun offered up is to start with a brushcutter. They come with much larger cc motors than weedeaters and make a simple ,lightweight more powerful mini-longtail conversion. examp. www.Duropower.com offers a 51.7cc brushcutter for $179.00.
     
  11. smoothseas200
    Joined: Feb 2008
    Posts: 11
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    Location: Alabama

    smoothseas200 Junior Member

    Lightweight Weedtrimmer Outboard Plans

    Hello Everyone,

    I have the plans for this conversion for sale on Ebay. Many thanks to
    evlfkrjohn for referring me to this site. This is a proven design, take the time to read the entire ad as it is a bit lengthy but well worth your time. It has been designed as simply as possible. Please see Ebay Ads :
    250217316299 and 250217516279, both are my ads and both ads represent the same plans. This little motor will get the job done ! Who ever thought a weedeater could be this much fun !

    Thank you,

    Dean / jeta2008@netcommander.com
     
    Last edited: Feb 24, 2008
  12. smoothseas200
    Joined: Feb 2008
    Posts: 11
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    Location: Alabama

    smoothseas200 Junior Member

    Hello,
    I am new to this site and I have posted my Ebay Listing Numbers to purchase the plans for a proven, easy to build, lightweigt Weedtrimmer Outboard using a 31cc engine. Anything less is fruitless. I spent a fortune in the design of this outboard. Please see the ads, this is your answer to your problems. This is the design evlfkrjohn was refferring to. I am a Aeronautical eng, so I crunched some numbers and created this little monster. It can handle a 24' sailboat with ease and larger, and cost around $ 140.00 to build as "New".
    I wish you the very best, please let me know if I can help.
    Sincerely,
    Dean
    jeta2008@netcommander,com
     
  13. realmanofgenius
    Joined: Feb 2008
    Posts: 2
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    Location: St. Louis, MO

    realmanofgenius New Member

    I've been using this site as a reference and have tried making one of these darn things but have hit some snags. First of all I tried to keep the lower gearbox on my Stihl FS85 trimmer/brushcutter. The problem that I experienced with this is that the force of the water being pushed by the prop would push it deeper and deeper into the water. To correct this problem I need to either shorten the shaft to about 35" so that the prop is pointing more horizontal, or I need to take off the gearbox and have the prop directly off the back of the driveshaft. I would like to have the prop directly off of the driveshaft but am stumped on how to do so without my driveshaft sliding out the back end??? Any help would be much appreciated!!!
     
  14. crokseti
    Joined: Feb 2008
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    Location: gainesville ga.

    crokseti New Member

    Ive almost got one built and am waiting for the prop from Youngs.
    Cant wait to try it.
     

  15. crokseti
    Joined: Feb 2008
    Posts: 4
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    Location: gainesville ga.

    crokseti New Member

    I made my shaft out of 1 in. pipe and inserted a bearing in either end.
    Had to ream it out a little to accept it but its snug. Then I used set screws to hold the gearbox and motor on the shaft.
    I sealed the gearbox as best I could with form-a-gasket and painted the whole thing with hammertough paint.
    I added grease fittings in the gearbox and the shaft also.
    Come on Young's.
     
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