Homemade outboard

[maxum247]

Re: Homemade outboard

The blade acts as a flywheel there and adds some mass and momentum to the light engine in those cases.

Any idea's for countering the problem of kick back when pull starting the engine as the blade is no longer there to act as a flywheel to balance things out, say a cast iron flywheel wasn't available for the engine being used?
Or will the driveshaft in the lower unit usually be enough to offset the difference of the blade not being there and act as a flywheel allowing the use of a regular light weight flywheel that comes on alot of the newer push mower engines?

max!

 

[weldbilt17]

Re: Homemade outboard

OK im completely new to this homemade outboard thing but it looks so fun.. I have an extra old 5.5 hp evinrude lower end from the sixties.. I parted it out to finish restoring my other 63 evinrude just like it.. But Im thinkin I should try to put a mower engine on top of the extra leg.. How exactly do you mount the motor to the leg.. I understand using a coupling and pins of some type to attach the shafts. but You made a plate with the bolt patterns of the lower end.. and it also mounted the engine?

The one I made is chain driven, but a belt drive or direct drive will work to. The only reason that I chose a chain was to get the motor down closer to the lower unit and move it back to have room for the gas tank because it is gravity feed and I did'nt what a fuel pump on it. If you go that route try to use thr crankshaft end to make an adapter out of because the input shaft on the lower unit is hardened and almost impossible to drill unless you have a carbide bit to do it with. The adapter plate was 1/4 '' steel or alluminum mated to the lower unit and to whatever engine you use.

 

[testmoron]

Re: Homemade outboard

If the points are set right, that engine will not kick back.

 

[Chris's CVX16]

Re: Homemade outboard

Not to get completely off on a tangent but how about making it a hybrid?

Use the lawn type motor to turn some kind of generator or alternator to directly charge/recharge a battery. Then make yourself an all electric outboard. I don't know what motor you might be able to use but I bet there are 12 volt motors out there that are very powerful and easy enough to run across. Maybe even a car starter if you can keep it cool enough and find a way to use the gear to drive some small flywheel.

 

[maxum247]

Re: Homemade outboard

If the points are set right, that engine will not kick back.

Thanks!

max!

 

[weldbilt17]

Re: Homemade outboard

It's been awhile guys. The motor that I built has two seperate plates, one mounts to the lower unit and the other is matted to the engine. I built spacers to give the clearance I needed for a belt drive from the motor to the lower unit. I also had to offset the motor toward the rear of the lower unit for the seperation I needed for the pulleys. Good measurements are key to lining it all up. I'll try to get some pics of it broke down.

 

[bigred8033]

Re: Homemade outboard

I'm In the middle of building my 2nd lawnmower outboard first was a 5hp briggs mounted on a old 5 hp buckeneer lower and now working on a 13 hp briggs mounted on a 8hp suzuki lower should have it done in few days ready to try out, I am trying to decide if i should weld my shaft adapter to the lower unit or drill it and put in a shear pin. Any thoughts on it?

 

[RRitt]

Re: Homemade outboard

Please post picks. Especially pictures that show what problems and solutions you faced building it.

 

[weldbilt17]

Re: Homemade outboard

I'm In the middle of building my 2nd lawnmower outboard first was a 5hp briggs mounted on a old 5 hp buckeneer lower and now working on a 13 hp briggs mounted on a 8hp suzuki lower should have it done in few days ready to try out, I am trying to decide if i should weld my shaft adapter to the lower unit or drill it and put in a shear pin. Any thoughts on it?

The one I have now I used the crankshaft end from the original motor and welded an extension on to accept a bearing and made a bearing holder and spacers for a timming pulley to drive the main shaft.

 

[RRitt]

Re: Homemade outboard

I just bought an old 10HP 2 stroke mariner. I'll throw away the engine and keep the gearleg. I figure if I keep the mariner engine pan then i have tiller, throttle, and gearshift mechanisms.

1. do briggs engines need gravity to feed the carbs or do they have some form of fuel pump? If not briggs what about tecumseh or honda?

2. has anybody tried a simple hollow rod coupler with set screws to tie the engine crank onto the driveshaft?

what other basic issues came up?

 

[garzilla]

Re: Homemade outboard

I just bought an old 10HP 2 stroke mariner. I'll throw away the engine and keep the gearleg. I figure if I keep the mariner engine pan then i have tiller, throttle, and gearshift mechanisms.

1. do briggs engines need gravity to feed the carbs or do they have some form of fuel pump? If not briggs what about tecumseh or honda?

2. has anybody tried a simple hollow rod coupler with set screws to tie the engine crank onto the driveshaft?

what other basic issues came up?

As far as I know....the smaller briggs motors do have a diaphragm type pump, the type of setup where the carb is basically attached to the gas tank. Would that be enough to draw up a hose from a floor mounted tank??? Doubtful.

I'm also working on the same project....sears 9.9 lower with a 5.5hp Briggs.
Sears motor was shot, so I took apart the motor, took the crank to a buddies steel shop and cut off the splined end of the crank that mated to the driveshaft.

Took the Briggs "adapter" that mated the motors crank end, to the blade, cut off the end that I didn't need, and welded the two together.

All I need to do now, is find a lathe, and turn it to be sure it's perfectly true...make a plate to bolt to the top of the lower leg, some long bolts and I should be cruising.....once I also find a prop for this sears outboard..

I bypassed all the governors on the mower, and redid the mowers existing throttle and this thing will idle SUPER low now...I mean like bang.......bang..........bang......idle.
Perfect for shifting.

On the other side of the coin however....this motor will also rev until I'd let it throw itself apart....which would convinently be at face level.



Bring along a 5 gallon gas can with you and I'd imagine you could cruise for a while.

 

[steelespike]

Re: Homemade outboard

The 5 hp Briggs outboard has a governor.As I understand it these motors don't like to over rev.

 

[garzilla]

Re: Homemade outboard

The 5 hp Briggs outboard has a governor.As I understand it these motors don't like to over rev.

Nope, they don't. But bypassing all that to get a nice shiftable low idle, unfortunately will also let itself grenade if you're not careful.
I can't imagine it getting too crazy once the motors in the water though....but thats yet to be seen.

 

[Mark42]

Re: Homemade outboard

I wouldn't worry too much about over-revving it. These motors tend to get bad valve float before they break a rod (assuming its got oil and not worn badly). And with the load of the prop, it should be fine. Although I prefer Tecumseh motors for high revs. BTW, if you need a simple vacuum operated fuel pump, look at the one Briggs used on the 18 hp opposed twins. Cheap and bullet-proof.

 

[RRitt]

Re: Homemade outboard

I'm not sure why you would go to all that trouble to build a 5HP version. You can buy a brand new 5hp briggs outboard direct from the factory for about $700 - or less. I bought one and it's the most awesome little mangrove motor I've ever seen. Its noisy, it vibrates, and it doesn't have a lots of RPM ... but its indestructible. It's the perfect flats boat outboard because if you can see water then it's deep enough to go there. Except that 5HP isn't enough power. But we'll see about that.

 

[weldbilt17]

Re: Homemade outboard

Ive got some pics of my new engine I put together if I can firgure out how to get them on here

 

[RRitt]

Re: Homemade outboard

pics would be great. maybe a few shots of how you handled the drive shaft and engine mounts. i can hardly wait to get started on mine.

 

[dryguy]

Re: Homemade outboard

cool maybe ill hack up the lawn mower or electric weed wacker. lol

 

[RRitt]

Re: Homemade outboard

i talked to the guy who owns "ye old boat store" up on lafayette street. Back in the days before manateee huggers and epa regulations the popular fishing boat out on pine island used briggs. But they would mount them as an inboard. He said they were called beckboats. He painted the picture of a fishing jon with a 20-30 horse briggs hard mounted on a stand with a through-hull drive shaft. Apparently they were a dominant fishing boat back in the days when we had more fishermen than tourists.

How would you steer it and why would that be better than a long-tail mud motor or an air cooled outboard?

 

[chuckloveless]

Re: Homemade outboard

I have a Sears Gamefisher 1.2HP that I would like to put a 3hp vertical powerhead on. Any idea if I will need a special adapter/adapter plate for it? Could this be rather easily done?