Weed eater engine conversion

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

  1. rmenasco
    Joined: May 2010
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    Location: Florida

    rmenasco Junior Member

    I only need 3-4 inches for it to run in, the Motor is a 49cc mini-bike motor.
     
  2. Locked Up
    Joined: Oct 2011
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    Locked Up Junior Member

    New Member

    Hey all....

    Been workin on a project at the house for my final attack layout boat. Just on a wim, I did a search for weed eater boat motor and it brought me here. I am pleased to see there is so much interest in the same thing I am working on. I have reviewed some of the pictures on here at the mounting system everyone is using. This is where I am at on my project. I am currently working on an idea on here that I did not come across in the pictures. As soon as I get it mounted I will be sure to post pictures of the design. It will work like a dream and be very user friendly and very convenient on what it will have to offer. But I want to share as a completed picture, not words....I can't imagine how confusing it would be to put into words. Yet the pictures will make it so easy. I know I am rambling but I am just excited to see what this forum has to offer and what I am able to share !!!

    Pictures should be soon to follow......

    Thanks,
    John
     
  3. hoytedow
    Joined: Sep 2009
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    hoytedow Wood Butcher

    Welcome to the forum, John.
     
  4. Locked Up
    Joined: Oct 2011
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    Locked Up Junior Member

    shaft improvments

    currently I am using a stock aluminium shaft....however, I want to upgrade to stronger shaft....at minimum 3/4" conduit....but would consider stainless if I can figure out one thing.........

    Inside the stock shaft is an "inner cylinder" if you will, that carries/guides the flexible driveshaft. What are my options for replacing the aluminum shaft with a more robust shaft? Basically, how do I extract the sleeve from the current shaft to re-insert into conduit?...or do I need to do so at all?

    Would a better approach be to just use a single upper and lower sealed bearing in a 3/4" conduit? Instead of the flexible drive shaft should a replace with 5/16 rod as the drive shaft and modify the clutch and gear box on the end to accept the 5/16" "new" drive shaft?

    Or will I be just fine with the aluminum shaft and flexible drive shaft....just simply reinforce the aluminum shaft with external framing and call it good?

    my biggest concerns are hitting something under the water and ......

    A.) ripping the shaft from the motor
    B.) kinking the shaft beyond operation
    C.)ripping gearbox from the end of the shaft
    D.)ripping the prop from the gearbox
     
  5. Erich_870
    Joined: Feb 2009
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    Location: Juneau, Alaska

    Erich_870 Junior Member

    I think you're confusing a couple of terms. Specifically difference between the shaft and the shaft housing or tube.

    If I understand your question correctly, you currently have a wound wire shaft inside your aluminum shaft housing and you want to know if you should upgrade the wound wire for strength. The wound wire shaft is definitely a weak point but if you are really concerned about hitting your motor on something, you probably want to keep it. It has more spring to it and will absorb more energy then a solid shaft. That will reduce the damage to your prop or motor. Ripping anything off your motor could happen, but is pretty unlikely since you're not going that fast. With the wire shaft, bending the shaft tube won't automatically be a problem, as it's meant to operate in a bent shaft.

    For reference, I used the solid shaft on my motor. It's stronger than the wound wire, but it will transmit the forces of hitting something back up the motor.

    Hope that answered some of your questions.

    Erich
     
  6. Locked Up
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    Locked Up Junior Member

    My apologies for the lack of terms......OK here it goes......I know there is a flexible drive shaft, there are also 2 shaft tubes (one is slightly larger than the flexible drive shaft and the other is approx 3/4"). I am hoping to find out if there is a way to remove the smaller tube from the larger tube, to then install into stronger larger tube of my choice?

    Guys, my apologies again on the terms....around here if we don't already know the name of something....we name it whatever sounds good at the time !!! ha ha


    Thanks again all,

    John
     
  7. pistnbroke
    Joined: Jan 2009
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    Location: Noosa.Australia where god kissed the earth.

    pistnbroke I try

    on some of mine the inner liner is a plastic tube with fins..hole in the middle ..star shaped ..just pulls out
     
  8. Locked Up
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    Locked Up Junior Member

    Thanks Broke Piston,

    If I do get where I can pull it out.....do you think I would be able to reinstall it into another, stronger, outter tube....ie 3/4" conduit?
     
  9. pistnbroke
    Joined: Jan 2009
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    Location: Noosa.Australia where god kissed the earth.

    pistnbroke I try

    why not just put the whole thing inside another tube and pin it with some allen grub screws
     
  10. Locked Up
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    Locked Up Junior Member

    now that is some good thinkin' ....then build a cone in front of the gear box


    THANK YOU !!!!!!
     
  11. Erich_870
    Joined: Feb 2009
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    Location: Juneau, Alaska

    Erich_870 Junior Member

    It's not problem, it just helps the discussion if everyone is on the same page when we discuss parts and how to redesign stuff.

    I too have a plastic tube with fins. What is the outside diameter of your shaft housing? Mine’s 1", so stepping down to 3/4" would make no sense. The aluminum tube with this plastic liner inside is very strong. You could remove the plastic liner and replace it with bronze bushings if you needed to run a larger diameter shaft, but if you are thinking of just going to a solid shaft of the same size, then you can keep the liner.

    Erich
     
  12. notsofast
    Joined: Nov 2009
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    Location: Philippines

    notsofast Junior Member

    Lube

    I am building a 6.5Hp (Honda-clone) long tail. Prop shaft is SS 5/8" diameter 8' long. I know I need to support this with several bushings otherwise it will whip. I will follow the 40-20-rule. For the bushings I intend to use wood. Some questions:
    1. How often do I need to grease the bushings? Is once every 10 hours running time enough?
    2. Do I put grease fittings on every bush? If not, do I fill the entire shaft housing with grease?
    3. Cutlass bearing is at the prop end. Do I need to make a hole forward of the bearing so water will flow through it? I will rely on forward motion of the boat to force the water through the cutlass.
    4. Will oil suffice instead of grease? I can inject gear oil near the engine-end and just hope it will flow to the other bushings? =)

    Thanks.
     
  13. pistnbroke
    Joined: Jan 2009
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    Location: Noosa.Australia where god kissed the earth.

    pistnbroke I try

    wood on a small motor like this .....??? Look at my design with sealed thrust bearing and ball at the top ..plain bush in the middle ...if you must use hardwood then soak in light oil for many months and yes fit a gease nipple and groove the bearing to get it right in there ..
     
  14. Wavewacker
    Joined: Aug 2010
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    Location: Springfield, Mo.

    Wavewacker Senior Member

    I'm late to this dance, but IMO, I would not begin with a weedeater, I thought about it for my canoe and kayak.

    I have 4 of them in my garage, all broken except for one old one that has a briggs-starton and was built probably in the late 60s.

    I'd start from scratch, stronger tubbing, heavy duty industrial flexible shaft, bearings and a heavier briggs engine, 2.5 or 5 hp. The bigger heavier engine is not so much for the hp but something that can last, run longer.

    Wait til you're on the water and you yank on that weedeater and the recoil starter strips out and breaks.....plastic! And, you might think they sip gas, but I really don't think they are too efficient as they have to run at higher rpms to get enough power to turn a prop, even off a trolling motor.
     

  15. Mark Wo
    Joined: Dec 2007
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    Location: Minnesota

    Mark Wo Senior Member

    Wow, never built one nor run one and and yet confidently telling those of us who have built many and run them for years that we don't know what we are talking about. Amazing. This post reminds me of all the people who said these would never work when some of us had been running them for a year or more. Even had pictures showing thes homebuilts on our boats making waves and people were still saying they wouldn't work.

    The one I have utilizing the Honda GX35 motor is an amazing unit. That sucker can go amost a whole duck season for me on ONE tank of gas. Yup that's right, one tank of gas for the season. Now I don't use this combination everytime I hunt but do get out several times and put on many miles.

    I'd be careful saying what you did on a site like this. MANY people have built these things and they run very well for the purpose in which they were built.

    Mark
     
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