Weed eater engine conversion

For ben2go

Hi,

is this the type of Briggs & Stratton motor you are referring to? http://www.smallenginesuppliers.com/shop/html/pages/products/briggs_vertical_shaft_engines4299.html

I wonder how difficult it would be to mount it onto an outboard casing?

Regards.

Mark

 

Just a quick though and I don't know if it's been mentioned already somewhere deep in a post, but - pollution.

Is it that good an idea sticking a 2-stroke motor's exhaust pipe in the water and leaving a nice oily trail? I know in France they'd have you torpedoed - 4 stroke only here.

 

Sometimes a picture will suffice for a thousand words. Mark Wollner of Minneapolis Minn. is shown in testing his recently recently completed Duropower brushcutter surface drive conversion on his Hoefgen duck boat. Mark says he attained a GPS measured speed of 6.2 mph. The motor on Mark`s long tail is a box stock unmodified unit rated at 2 hp. Mark stated the motor had more than adequate power throughout the rpm range. If you zoom in you can see him smiling .

 

All 2 strokes are banned from SJWD lakes.No exceptions.Technology doesn't exsist in South Carolina.What's a campooter?Ya'll ever heard of such a thang?TV?Ain't that one of dem dar pictour boxes?I hate the south eastern US.

 

Looks simuliar but the shaft is way different than the one in the link.My shaft is straight 1/2 inch in diameter and 1 and 1/4 inches long with a 1/4 inch keyway.I think it is specific to Murray push mowers.Also the throttle has been locked out to hold the engine at the max torque rpm.Basicly they set the rpm where they want it and bent a tab down on the throttle arm and used a stiff spring to hold it there.

 

New to the forum, but I have been viewing for some time... Have a question that I offer anyone to answer. Besides the obvious (handle and mount), what must be done to the shaft of a weed eater besides the placement of the prop?


John O'Neal
I want to build something like your longtail. I am also looking for the most simple thing thing I can (no gear reduction like has been mentioned). Must I follow the details that "ripped off" provided, or is there an easier way (limited on cash)

 

Hello JKwhite, WELCOME!!!! I'm no pro. but I just built one pretty much just like ripped off's version. I assume in you question you mean tube that encompasses the shaft.
You got to seal it. Ripped off used grease seals but John Oneal said he used sealed radial bearings. Hey John where do you get those?

You may not have to but I think it's a good idea to weld a skeg to it as well. John could answer that better. In his earlier pics he has some of a moter with no skeg. Also a bigger prop.

 

I also was hoping turn4fun...ripped off could get on here and answer this question...or maybe John could?

I was thinking of building a bigger moter with a 3 or 4 hp engine. I found a few guys that already build them. (stump jumper 4hp, utah marsh moters 7hp) I asked how fast I would go in a Otter 2000 boat. They said 8 to 10mph. Well I'm doing 8 now with my 34.5cc briggs. So is it no better to build a bigger moter? I know ripped off built some real nice looking ones cause I saw them on a different site. What is your opinion Ripped off?

 

Seals do make sense, that's what I was wondering. I too have an Otter (mine is the 1200). I have some plans drawn up for a mount. Since the backs are the same on the 2000 and 1200, could you take a look at them and give me a sanity check. I will try and get them uploaded this evening.

Back on the prop. I have the link to Young's. Are there any special mods for its attachment? It kinda looks rather easy.

Thanks for the info.

 

If the hull is not designed to plane, or if it is designed to plane but it doesn't have enough HP to plane, you will not go faster with a bigger engine.

You should figure 1 HP for every 50 pounds to make a boat plane. With less than this amount of power the boat is probably going to run only at 'hull speed' and it only takes 1 HP for every 500 pounds to push a boat at hull speed.

 

boat=130lbs
+ Me= 240lbs
+ gear= 150lbs
--------------
520 pounds ...wow that would be at least a 10 horse moter which would be to heavy for my little boat. The 6hp robin set ups weigh around 70lbs. I guess the weedeater route is the way to go. My moter works great now. Very reliable. Thanks again Ripped off and thanks John Oneil for all your ideas. I'm hooked and am still going to make a bigger one out of the duropower head. If I come up with anything usefull I'll post it.

 

JK; If you could find a used brushcutter or possibly one from a pawn shop it may provide you with the simplest ,easiest and most cost effective conversion. All the things that you will need come on a brushcutter( controls, a boom with multiple carrier bearings, and a steel drive shaft ). The motors on brush cutters are usually larger than most weed eaters and provide more torque. A good thing. You will need to remove the gear head and make, or have made, the bushing seal combination at the prop end of the boom. The Youngs` props can generally be attached with a roll pin. Fastenal has bronze flange bearings in 5/16" id & 3/8 " id for less than $ 3 for a pack of 5. National oil seals can be obtained from almost any auto pts. store. I got mine at NAPA. Here are the numbers for the oil seals. 5/16" id .750 od National # 3140-350364 3/8" id .750 od National # 3687-330385. Starting with a brand new brushcutter unit you can figure you will probably add $50 to $75 to convert it to a mini-long tail. Mine cost $300 to build $250 was for the cost of a new brushcutter. I have posted a sketch of the bearing & seal combination I made for the prop end of my motor. It use two flange bearings and two seals. I pack it with marine grease. With the drive shaft installed it becomes a sealed unit. Good luck with your build.
Wac m : I did use a 7/8" od X 3/8" radial ball bearing on my ryobi powered unit . You can buy those bearings several places Internet vendors ,Fastenal, bearing dist. I used them only once because you have to use bearing shaft with that type of bearing. Bearing shaft is ground 1/2 to 1 1/2 thou. smaller so it will go through the radial bearing. I couldn`t find a local supplier so I had to order it on the net. The cost plus shipping just wasn`t worth it.

 

Hey John is that a Youngs prop in your first pic you posted with the moter with no skeg? It looks bigger then a T10 or 12. How did it do? I noticed the newer moters all have skegs now and smaller props so I'm curious what happened?

Is the Chinese brushcutter shaft solid? stainless?

Thanks!!

 

Hey JK, I used a peice of 2in angle and bolted it to the storage cover on my stealth 2000. It works ok but I want to get it a bit higher.
Check this guys idea out on the Utah Marsh moter. Looks pretty solid. I'm going to do something simular but raise it a foot. I'll post it when I'm done. I love the oarlock idea Ripped Off made. It works great and its so simple.
http://utahmarshmotors.com/plugins/albums/slideshow/slideshow.html

 

Wac-m ; The prop you reference was a T-10. It worked great but I destroyed it. Investment cast alum. is brittle and doesn`t have the strength forged alum. It broke easily. I replaced it with the t-12 you see pictured in a later post and added a skeg. I broke the T-12 also but that was my fault. I now have a composite prop off of a Shakespeare Wonder troll it`s tougher than Chinese arithmetic. Young's` makes it in a alum. version, it`s the T-4.
The shaft of the Chinese (Duropower) brushcutter is a hardened steel shaft(not stainless) splined on both ends. It has a .314 od.