Weed eater engine conversion

[SSNgineer]

Okay, so I tested my first prototype, based on a Homelite Trim Lite 26cc trimmer that I got at a tool sale for $40. It has a 7/8 aluminum tube, so I had to modify it a bit to work. I JB welded a 1" dia. section onto the cut down 7/8 shaft and then welded a 90 degree 3/4" electrical conduit elbow at the end. I made a skeg and two more veins and spaced them 120 degrees apart. I will later mount a duct on these to straighten and direct the flow to the prop. I turned the trimmer output shaft down and made an aluminum tapered cone to go down to 1/2" dia. I am using an Octura 0977 prop, which has a 2.7" pitch and is just over 3" dia. The transom clamp is two small c-clamps JB welded into grooves on the trimmer handle. a piece of copper pipe is used as a bushing between the handle and the shaft. I have yet to finish the tiller, but will use the lower section of 7/8 tube cut off of the trimmer, the foam rubber handle removed from the top section, and a bicycle brake handle salvaged from an old scooter.

I ran it in a garbage can today and it made very impressive thrust. It will start right up with the prop in the water and idles nicely. I noticed some cavitation coming off the center of the prop shaft under power, so I made a nice little tapered cone to screw on after the prop. I found a .120" thick polycarbonate glass at Walmart tonight for < $2 which I will cut up and make into a duct or Kort nozzle to preload the prop. Hopefully this will eliminate any cavitation and improve the efficiency a bit.

The gear driven version based on a grinder is still in the works. The direct drive prototype was the quickest to build, so I am finishing it first. I have a little more machining to do on the new housing before attaching the main shaft tube.

Also, I bought a rusted up 1954 3HP Hiawatha outboard with a very lightweight, usable lower unit. It has a 1.7:1 reduction and a water pump if I want to do water cooling. Also, I can run the exhaust straight through the fairing. That combined with an adjustable transom clamp should prove to be a nice little combination to mount a trimmer powerhead. I will try to post pics soon.

[smoothseas200]

Hello everyone, I have a time tested proven design that can easily be built just like a brand new outboard for $ 140 - $ 160. I supply parts lists, and the vendors. The plans are easily laid out with drawings, dimensions, and written instructions. After gathering the parts you can build this outboard in 8-10 hours. This is simply the way to go, once you hit the throttle I guarantee you will smile. All "Bugs" have been eliminated, period. Alot of time and money went into the developement to get it RIGHT ! I am selling these plans for $9.95 a set and will be delivered directly to your computer in PDF format, so you can have the plans in a few minutes. Just remit a Postal Money Order for $9.95 made out to R.D. Moss and mail to :

R.D. Moss
261 Julia Circle Apt 15
Sulligent, Alabama 35586

Please be sure to include your email address with your Money Order, as I will send the plans instantly after reciept.

All inquiries please direct to : jeta2008@netcommander.com





19608

[mmartin]

Hey Guys,

I have thought about using a weedeater to make an inboard or staraight shaft mud motor. But why use those wimpy ones when you can get a brand new surplus 4hp Tecumseh, horizontal shaft engine for $ 120.00 from these guys: http://www.surpluscenter.com

It could be easily mounted and speed reduced like this site does:
http://www.asmomarine.com

I have not done one like this, but It should work and have plenty of power, unlike those little 33 cc jobs. It could be skeg mounted as well on a little launch. If anyone tries this let me know how it works.

Ps new memeber, first post!

[mmartin]

I just made the conversion. The 4 hp Tecumseh engine I mentioned is 5.2 cubic inches which works out to 85.2 cc. @ 3600 rpm, wt. is 15 lbs. There are also two models available for less money in a vertical shaft version, same hp (4).

[Orphanedcowboy]

One thing I need to clarify, mainly for my conscience.

I saw a very similar set-up and copied it with out thought, I am not trying to pass this off as my design, I built it then realized I had seen the original while researching this. Look for a post by Caveman on page 4 of this thread.


I just finished it this morning. I built this with the Hybrid Series of boats in mind, but it should work fine with any small 8' - 10" pontoon style bass buggy. You can use a piece of angle iron clamped to the transom with a hole for the caster swivel.

Please let me know what you think, thanks!

Weed Wacker Build Notes:

Brushcutter:

Ryobi BC30

Engine Construction: 2-Cycle
Engine Displacement (cc): 30 cc
Engine Torque (Ft. /Lb.): 0
Fuel Mix Ratio: 50:1
Fuel Tank Capacity (Gal): 1 Gal
Fuel Type: Gas & Oil Mix
Horsepower: 1 HP
Assembled Weight: Less than 15 lbs with fuel

Caster Swivel $6 @ Ace Hardware
1" Shaft Collars $7 @ Ace Hardware
1/2" ID x 1 1/8" long Steel Bushing $2 @ Ace Hardware
5/16" ID 1/2" OD x 3/4 long Plastic Bushing $.60 @ Ace Hardware
Young’s Prop T-8 Prop $18 @ eBay
Throttle Cables: $1-$8 on eBay, be sure to check the length
Throttle Handle/Lever: $11 on eBay, lever was for a Stihl FS 80
Tiller Handle: $3 1/2” metal conduit from Lowe's
Handle Bracket/Cross Block: Free/Came with the Brushcutter

The first thing you will need to do is remove the upper shaft. It is held in place with a #10 screw and a bolt thru the lower part of the housing that holds the throttle cable and kill switch in place. Be sure to keep the spring located inside the upper shaft around the drive shaft. Keep the upper shaft; you will use it as a jig to make your motor mount.

The lower shaft will need to be modified to fit the housing. The upper shaft has a slot that clocks it’s orientation in relation to the housing. This slot will need to be added to the lower shaft. The shaft will need to be clocked in order to make sure the prop will be in the correct location. Use a marker to mark the tab inside the housing.

Then push the un-modified lower shaft into the housing and mark it. Use a dremel to cut the slot, once the slot is the correct depth, drill the hole for the retainer screw. Be careful not to drill the drive shaft inside the housing. Remove the lower shaft from the housing, and place the spring around the drift shaft. Re-install the lower shaft, install the retainer screw and the lower housing bolt, then tighten both, making sure no to over-tighten the 2 screws.
To make the mount use the upper shaft that you removed for your jig. Put both split lock collars on the shaft and orientate the bolts and use a belt sander to make the opposite side flat. I used 4” spacing on the collars after they were modified and welded the 1” wide flat strap on. Weld on the 1/2” steel bushing, I used a 60/40 offset on the pivot bushing, this way if I cannot get the desired angle I can rotate the mount. The plastic bushings will need to be ground to an overall width of 1 1/8”. Let everything cool then remove the mount from your jig, prep for paint, install the plastic bushings and then install on your weed wacker motor.

I used a T-8 prop from Young's Props, http://www.youngprops.com/ mounted to the original string trimmer head bolt that came with the brush cutter. The diameter is 3/8” and is the same diameter as the hole in the prop. Slide the prop all the way down against the hexagon shoulder and then carefully drill the 1/8” diameter roll pin hole. The prop is significantly softer than the shaft, so do yourself a favor and use a sharp drill and a drill press if possible. Once you have the hole drilled and the roll pin installed, cut off the shaft 1/8” longer than the prop body. This will allow you to tell if there is a problem later on down the road, and it will also fully support the prop.

Next you will need to figure out your throttle and tiller handle. I choose to use the cross block/ handle mount hat came with the Brushcutter. I am still in the process of perfecting this for the Hybrid. I found throttle cables on eBay ranging from $1 to $8, figure out your length and your throttle control, twist, lever, etc. I went with a lever off of a Stihl FS 80 weed eater. Once you have your length, then you will need your angle for your tiller handle, I did this by mounting mine to my bench, then figuring out the desired prop angle I wanted.

Now your ready to make your throttle, determine what style you want, I tried a twist throttle off of a zipper scooter and wasn’t impressed. I then spent 2 weeks looking for throttle levers, spent about $100 on weed eater handlebar mounted throttle handles only to find out I liked the plain ole bicycle brake lever style. The lever I used is off of a Stihl Weed eater model FS80. This is the older style, not the newer style plastic molded lever. I decided on which cable length I needed and made the necessary modifications to fit my application. The Ryobi weed eater uses a “Z” style cable end, and most cables will be a barrel type end. I simply cut the end off of the cable and threaded it thru the old cable mount, determined my length, cut the cable again and crimped a #10 ring terminal on the cable. I then used a #8 bolt and two nuts mounted on either side of the carburetor throttle arm, and tightened down snug.

I plan on going back and soldering the ring terminal to the cable, replacing all the bolts with stainless bolts and putting Loctite on all them. I also will be painting this after I test it on a couple of jon boats, a 14' and a 10' against a 30 lb Minn Kota trolling motor. I also need to mount the kill switch, but I haven't found anything I like, but this is a small problem.

You should now be ready to test it out.

Here is a slide show of the build:

[Orphanedcowboy]

Originally Posted by smoothseas200

Hello everyone, I have a time tested proven design that can easily be built just like a brand new outboard for $ 140 - $ 160. I supply parts lists, and the vendors. The plans are easily laid out with drawings, dimensions, and written instructions. After gathering the parts you can build this outboard in 8-10 hours. This is simply the way to go, once you hit the throttle I guarantee you will smile. All "Bugs" have been eliminated, period. Alot of time and money went into the developement to get it RIGHT ! I am selling these plans for $9.95 a set and will be delivered directly to your computer in PDF format, so you can have the plans in a few minutes. Just remit a Postal Money Order for $9.95 made out to R.D. Moss and mail to :

R.D. Moss
261 Julia Circle Apt 15
Sulligent, Alabama 35586

Please be sure to include your email address with your Money Order, as I will send the plans instantly after reciept.

All inquiries please direct to : jeta2008@netcommander.com

Attachment 1960819608

Southseas, This is a copy of Turn4fun/Ripped Off's design, he posted these pictures last year on another forum. Also Island Hoper Outboards has been building these for some time, nothing new and definately nothing worth paying for. I built one off of Turn4fun/Ripped Off's design and if anyone wants the plans I will give them away for FREE, just as Turn4fun/Ripped Off has done.

[superstitch626]

Hello all this is my first post i have another source for props you can get Composite Props instead of aluminum ones http://www.smalloutboardengines.com/ has them in their parts section i have been told that these types of props are lighter and stronger than the aluminum ones. i have also been searchings the possibility of use of one of these for my potaboat but instead of using the stock gear box what do you guys think about using a angle grinder? i have seen a couple of other posts about this and im going to try and figure this stuff out.

[smoothseas200]

Hello Orphaned Cowboy,
I appreciate your criticism, but if you take the time to look at the gear box you will notice the photo you presented is nothing more than a standard weedeater gearbox turning a very small prop. My design is powerful because of the gear reduction, and is equipped with a larger 3 blade Motorguide machete aluminum prop. It is by far superior to the design you have shown, I know because I built this type during the developement of my final design several years ago and found it to be very low on power. Since you have made such an issue over paying $ 9.95 for my plans, I will offer the plans FREE to anyone that wants them just to PROOVE it is far more superior to the other designs. It is FASTER and more Powerful than any design you may have tried. You build it then come back to post your results for everyone to see.
Order the Plans at : jeta2008@netcommander.com

The Plans are FREE, Get them while you can. Alot of time, money and engineering went into this design. It was developed to achieve the maximum performance from the engine. The power is balanced from the engine to the gearbox, and finally to the large prop for a perfect blend of POWER. I am a Engineer so I know what I'm doing. I worked all off the numbers, rpm, gearbox speed and thrust test in a test tank. It puts out 8.8hp at the PROP !
ORDER THE PLANS ! THEY ARE FREE ! I KNOW MY TIME, MONEY AND EFFORT MEANS NOTHING TO YOU ! SO ORDER THE REAL DEAL NOW ! IT'S FREE ! NO MORE COMPLAINTS OK ? I have sold over 1000 of these on Ebay with NO COMPLAINTS - SMOOTHSEAS200

[Orphanedcowboy]

Mr. Moss, I don't have a problem with you making a buck. I can also respect your time and effort. But everyone who has ever contributed to this thread that has built or modified a weed eater has done so with considerable time and effort and expense. I have spent upwards of $1000 on everyday items that can be easily modified and used with out having to buy or build a gear box. I have tested the gear box on these motors for water intrusion, and it just isn't happening, so far. I have tested the motor shown on a 250+ lb 12' jon boat(the boat I plan on using it on weighs less than 80 lbs) and top speed was 3.5 mph, not flying but fast enough for me going up a river filled with stumps and trees in the dark. I have a few dollars over $200 in my first design not counting build and test time. Your design is far superior to mine, but I could care less, I built mine with little to no help from anyone else. I did take several designs and incorporate them into my final build, but we all did. This is nothing new and certainly we can all learn from each other. The beauty of these motors is simplicity. I am a duck hunter, not an engineer, but I work with several hundred engineers everyday and I can respect your time and effort you put into your education and your outboard. I just don't understand why you came into the thread and tried to peddle the plans instead of engaging people first. That is what I had a problem with.

[Orphanedcowboy]

If you use my plans you need to cut 7/16" off of the outer shaft to make sure you have enough drive shaft engagement in the clutch drive

I found out the hard way and sheared the drive shaft off, luckily I had a replacement................

[Orphanedcowboy]

Smoothseas200

Why haven't you replied to anyone who has asked for plans? I know of several that have asked, myself included and have heard nothing.

Better yet how many people do you think would buy them from this site? Your giving them away for free, I'll give you $50 to post them in this thread, problem solved.

[superstitch626]

Orphanedcowboy take a chill pill bro he sent me the designs when i asked for them. and no i am not a clone of him or something like that.

[kengrome]

Orphanedcowboy take a chill pill bro he sent me the designs when i asked for them.

He totally ignored both me and my friend, so it seems he is not willing to do what he promises.

[superstitch626]

well it took him couple of days and a couple of emails but i got it. don't know what to tell ya

[kengrome]

well it took him couple of days and a couple of emails but i got it. don't know what to tell ya

You don't have to tell me anything ...

His refusal to send the plans as promised the FIRST TIME he gets an email request tells me he is trying to avoid living up to his promise -- and that's all I need to know about him.

If he REALLY wanted to provide his plans for free he should attach them to a post in this thread so people can download them immediately. Then remove the attached file after a week or so when he is no longer willing to give them away for free. But instead he seems to prefer to play childish games by making people send multiple requests before he will bother to live up to his commitment.