Weed eater engine conversion

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

  1. z1ox
    Joined: Mar 2007
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    Location: bayou city

    z1ox New Member

    gear reduction trial

    How did your trial go on the gear reduction? Because of other threads on this topic concerning 'bogging down of the engine' I had felt a planetary gear reducer would be perfect. The specifications for an Echo 22.8cc weedeater model SRM230 engine has ~3000 RPM at Idle and ~12000 RPM wide open. Of course I wouldnt think of using anything less than 31cc for this, but the RPMs are probably going to be near this. (I am not taking this thing to the moon, anyway!) There are some planetary gear reducers out there that look like they may be compatable but I have not been able to find any on the web that could handle 12000 RPM input. I will keep looking.

    I am thinking a 3:1 gear reduction would generate more torque to allow a larger prop... I will study this some more and see what I find. The ones I have seen so far are $50-$150.

    Thanks for sharing all your secrets. It was your project pictures that got me hooked, the parts list was a great bonus.
     
  2. Jimideaman
    Joined: Apr 2007
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    Location: EAST IOWA

    Jimideaman Junior Member

    hi
    Has anyone built a mud motor using a 4-stroke gas trimmer ? Menards has a 26 cc trimmer on sale and they claim in their Ad. " provides more torque and power than two-cycle engine. It runs quieter ... ". I don't what brand it is can't tell from Ad.) The picture/text shows it to be a split-shaft / curved-shaft design. Tnx for any comments anyone has.
     
  3. paulieh
    Joined: May 2007
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    Location: new zealand

    paulieh New Member

    Hey guys I'm just new to this website and are not sure how to add new post. My question is I've got a small featherlite weed eater motor and wanting to make it into a fishing Kontiki. The motor had a curved shaft so I have streighten it out. But I would like to shorten it up slightly. The shaft has a spring that has a steel square pin that goes into the motor and into the porp end. My question is how do I short it ???? Cheers Paulie.
     
  4. ripped off
    Joined: Sep 2006
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    ripped off Junior Member

    I don't want to discourage you, but before you start building get rid of that Featherlite and get something thats at least 30 cc. The Featherlites don't have enough torque to turn even a tiny prop in the water. I know a guy who built built one off of my design and used a 17cc Featherlite. It would not run in the water period. You could start it up out of the water, but the second the prop touched the water it would kill the motor. Even if you revved it up first it would still kill it. I later came accross a 21cc Featherlite for free and tried it with the same results. The smallest motor that I've been able to build a successful troller from was 28cc and it had just barely enough torque to run in the water. I've had great success using 31cc motors.
     
  5. Jimideaman
    Joined: Apr 2007
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    Location: EAST IOWA

    Jimideaman Junior Member

    4-cycle weed trimmer

    I purchased (on sale) a Sears Craftsman Weedwacker No. 79616, 40cc 4-stroke. I'm thinking I'll fabricate an extension to mate where the split shaft accepts attachments. If anyone has had experience with this particular model and had problems let me know and I can return it. If not, all I need is the time -- if anyone has any extra unused spare time hours, forward them. Jim
     
  6. flapdoodle
    Joined: Jul 2006
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    Location: Roswell, New Mexico

    flapdoodle Junior Member

  7. flapdoodle
    Joined: Jul 2006
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    Location: Roswell, New Mexico

    flapdoodle Junior Member

  8. John O`Neal
    Joined: Sep 2007
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    Location: Lenexa Ks.

    John O`Neal Junior Member

    weedeaters conversions work

    Ripped-off ; I have read your posts on this as well as other forums aka (turn4fun) and they have been both informative and enlightening . You have shortened the trial & error curve considerably. In a recent post a writer asked if the conversion displayed on the layout boat at the Cabelas waterfowl classic was one of yours ? It was my first attempt from two yrs. ago and it suffered from all the common problems, to small of an engine 25cc, and to large of a prop (Minn-kota plastic). It made a good fan for blowing the dust off the garage floor but hated water. I put it back on the shelf as duck season had arrived. I had essentially given up on it as an unfeasible idea. Then late one afternoon at the Four-Rivers wildlife area I followed a layout boat out of the marsh, he was using what I believe to be a unit of your design. The guy was tight lipped, wouldn`t give up an ounce of information, but I had seen what I needed to. The idea was workable I just needed the right parts. Bigger engine-smaller prop. At this point I decided to build my own version of your designed long shafted weedeater conversion. I took apart my cruise`carry outboard to get ideas. It is essentially a weedeater size engine in an outboard configuration. It uses an aluminum tube with a stainless steel 3/8" drive shaft running through nylon carrier bearings, this motor is over 20yrs. old and still works great so the design I figured is a sound one. For those of you out wanting to build one of these conversions here is how I built mine. I also arrived at 5ft. as the length of the carrier tube. This was determined based on the height of the transom (layout boat) and a desired shallow entry angle of the prop into the water. I used a 1 " tube with a .065 wall thickness. This allowed me utilize a 3/8" ID x 7/8 OD sealed ball bearing ($6) on the prop end . This combination creates a 5 thou. interference press fit. Works nicely for locating and holding the bearing. The carrier bearings (2) are made from 1" nylon rod. It`s cheap, durable and readily available from plastic supply houses. I got mine from Airparts in K.C.Ks.$4 a foot. I chucked the rod up in a lathe and center drilled it 3/8" . I then turned down the OD of the rod .0871 creating a 1 thou. interference press fit. I cut off 2 pieces each 1" long they will serve as the top bearing and the middle carrier bearing. I installed them using a long wooden dowel as an installation tool. The drive shaft just like Ripped-offs is 3/8 stainless rod. I had my buddy who has an end mill square off one end to fit into the engines output receiver. Any machine shop can preform this operation. I did my first one using 4 1/2" grinder with an abrasive flapper disc. I used a 3/8" set collar above the top bearing to prevent the shaft from sliding out of the carrier tube. On the prop end I also used a youngs 5 1/2" propeller . It mounts easily with a roll pen thru the 3/8" drive shaft. I use a small spacer washer between the prop and the roller bearing. This allows the prop when under load to press against the inner ball bearing race thus transferring the thrust up the carrier tube to the transom mount, as opposed to up the drive shaft to the engines crank shaft. All you need now is a powerhead. Pay heed to Ripped-offs advice and go with the larger cc motors it will save you some frustration. Ripped-offs versions were the first in the water and I certainly don`t intend to imply that I have built a better mousetrap. I`m just offering up a different way to get there. Ripped-off; I am anxiously awaiting news on your gear-reduction model. You might want to look at Rickshaw-motors.com he has a really slick unit. FYI Youngs makes props for clockwise as well as counter-clockwise rotation
     
  9. ripped off
    Joined: Sep 2006
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    ripped off Junior Member

    Great job John. That may very well have been me at 4-riv, I get approached at the ramp at unit 4 almost every time I'm out. I've thought about using delrin for my bearings several times but never have gotten around to it. In all the years mine has been in use, I have never had to replace one of my bronze bearings yet. I used to be very tight lipped about how they were made because I always thought I would have a go at marketing them, but just never had the money it takes to get something like that off the ground. Once the 5 & 6.5 mudbuddys came out they pretty much killed any potential market for the weedwackers anyway. I found the rickshaw site just a week ago, it's amazing how much it resembles one of mine. Interestingly enough, I always talked with my buddies about using that same Honda engine and a gear reduction unit. He's got a sweet looking design, but he also has way too much reduction and it shows. It says that his units are 3.75:1 all the testing I've done suggests that 2:1 is perfect. Post up a pic of your motor and I'll keep my eye out for ya in the marsh this season.
     
  10. John O`Neal
    Joined: Sep 2007
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    Location: Lenexa Ks.

    John O`Neal Junior Member

    weed-eater ingenuity

    Paintballer1244; If "ingenuity paves the path to achievement" you are certainly traveling the right road. Great design. I think we may have used the same brand C-clamp on the transom mount. I have since gotten a little lazy and started using old trolling motor mounts that I find at flea markets and garage sales. They look good and work great.------I have a question regarding your Bolens engine. I am currently putting together a long shaft weed-eater conversion for a friends layout boat and economy is a factor. I have seen the 31cc Bolens at Lowes for $69. Certainly reasonable enough for a new unit of that size. Since the pictures of your unit were posted last March I`m sure you have had an opportunity to use it . How did the Bolens work out ? Does it have adequate power ? Does it start and run well ? Does it have any negatives? Any information regarding this engine will be greatly appreciated.
     
  11. John O`Neal
    Joined: Sep 2007
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    Location: Lenexa Ks.

    John O`Neal Junior Member

    Weed-eater longshaft pictures

    Ripped off : Hope to have a camera soon capable of downloading to my computer. I`m looking forward to posting up some pics. As for seeing you in the marsh, I will keep an eye out for you I`m sure our paths will cross. Like yourself, I try to hunt as many days as possible. Regarding gear reduction units. I have started building one myself. I am already in my 2nd design and am currently waiting on bearings I ordered on the net. It will be belt driven HTD 480mm20mm8mm. I found some 2 to1 ratio pulleys (as per your testing)for next to nothing used. The pulleys come from the racing industry and are used on stock cars ,dirt modifieds, etc. They are abundant on the used market. I had hoped to have it ready to test within the month, but duck season is rapidly approaching, and as my wife says " you never get a d** thing done around here when those ducks start flying" If you see a white trailer, double layout stacker with a DU license plate in the parking lot at 4riv, keep an eye out I`m in the marsh.
     
  12. John O`Neal
    Joined: Sep 2007
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    Location: Lenexa Ks.

    John O`Neal Junior Member

    " ingenuity paves the path to achievement"
     
  13. rangersboat
    Joined: Nov 2007
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    Location: Texas

    rangersboat New Member

    I am working on something like this too, I have a roybi 31cc weed eater and I hope to put a prop on it to run my 12 ft boat. One question about go devils, does a 2 hp 4 cycle engine need a oil pump to be a go devil? Go devils run at angles so they might no get oil. any help would be nice.
     
  14. Syed
    Joined: Sep 2005
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    Location: Lahore, Pakistan

    Syed Member

    Sachs 309

    I have a SACHS 309 two stroke engine, starts and runs great. I do not know its power/cc ratings. Any help about its power rating will be appreciated as I want to enter into the arena of weed eater conversion.
    Thanks,
    Best,
     

  15. John O`Neal
    Joined: Sep 2007
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    Location: Lenexa Ks.

    John O`Neal Junior Member

    Weed-eater longshaft pictures

    My layout rig
     

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