Homemade outboard

[maxum247]

Has anyone ever built there own outboard motor? I've built three.
I used push lawn mower engines to a riding lawn mower engine that was an 8hp electric start that had forward, reverse and neutral gears. Used that thing for three years, made one heck of a motor for trolling, gas bill was cheap. Sold the boat and it was still running strong!
If you have been thinking about building one yourself, remember this, if it is a pull type engine off of a push mower make certain to use one that has a cast iron flywheel. The regular aluminum flywheel does,t work well, they will snatch back when you crank them and it hurts. I learned the hard way!
Just wondering if anyone else has built one. I've been wanting to build another one but haven't come across a good 6hp or 8hp lower unit. Lower units used to be pretty easy to find, but are getting hard to find, used to find them pretty readily around the neighborhood but don't see them to much these days.I,ve been looking for a couple years now!
This one would be a 12hp riding lawn mower engine with electric start. The bad part about these engines was I couldn't get to the docks to put over, someone would always come up and ask me all about it and how I built it! But you know that was really the fun of it.

 

[JB]

Re: Homemade outboard

Got pix?

 

[Drowned Rat]

Re: Homemade outboard

Would love to see how they look. How did they compare, power wise, to comparable sized regular outboards?

 

[maxum247]

Re: Homemade outboard

I don't, but if I build another I will take pictures of it.

 

[maxum247]

Re: Homemade outboard

The push mower version pretty much looks like a regular air cooled outboard, not the first time this has been done. The riding mower version look rather clunky, is clunky a word? As far as the performance, in my case I'd say if you build an 8hp it's more like a 6hp. Had my 8 on a heavy wooden 14 foot skiff. It would plane at what felt like about 12 or 13 mph.

 

[TOHATSU GURU]

Re: Homemade outboard

"The riding mower version look rather clunky, is clunky a word?"

I use it all the time...As in, my ex-wife is really clunky.

 

[weldbilt17]

Re: Homemade outboard

Hey, I'm am currently working on a project like that. I have a 8 hp briggs vetical shaft that I am adapting to a 35hp lower unit. I know that sounds like overkill but it surly should hold up. I have to finish the riser to mount the motor to the lower unit but I have a machinest at work so it shouldn't be a problem. My only consern is if the motor will have enough power. I think that there is enough room in there to mount a belt drive of some sort, but that would consist of a support bearing for the lower unit shaft. Anyway if it works like it sould I'll try to post some pictures.

 

[Lone Duck]

Re: Homemade outboard

How's the shaker ?

 

[Vlad D Impeller]

Re: Homemade outboard

How's the shaker ?

Ask Jimmy Buffet.

 

[weldbilt17]

Re: Homemade outboard

Here's a couple of pictures of the ol briggs&mercury engine I put together, not great but it functions hope to test it tomorrow.

 

[kenmyfam]

Re: Homemade outboard

Looks like fun !!!

 

[wbeaton]

Re: Homemade outboard

How topical. As I was looking at the ever corroding deck on my lawnmower yesterday I thought how much fun it would be to build an outboard out of it at the end of the season.

Do you have any photos of the project? How did you connect the crank to the driveshaft?

 

[Wee Hooker]

Re: Homemade outboard

I always thought there could be a decent market for a "make your own " outboard kit. i.e. Somebody could make/market a basic and lightweight lower end with universal mounting plate for 4-8 hp lawnmower engines. Drive couuld be via a flexable coupling shaft/sleve and control via a tiller arm and throttle kit.

 

[maxum247]

Re: Homemade outboard

Here's a couple of pictures of the ol briggs&mercury engine I put together, not great but it functions hope to test it tomorrow.View attachment 29223

Did you get a chance to test the briggs&mercury? If so how did it turn out?

max!

 

[weldbilt17]

Re: Homemade outboard

Did you get a chance to test the briggs&mercury? If so how did it turn out?

max!

Yes, I got my test done. It did work pretty well as far as forward and reverse, but the prop is a little bit to much for the motor. It would only go ( I'm guessing) about 10 mph, but it is a 35hp lower unit. I'm thinking maby a 10hp lower end would be more sufice for the little 8 hp briggs. It's too much water for the little guy to push, but I was happy because it did work. THANKS.

 

[weldbilt17]

Re: Homemade outboard

How topical. As I was looking at the ever corroding deck on my lawnmower yesterday I thought how much fun it would be to build an outboard out of it at the end of the season.

Do you have any photos of the project? How did you connect the crank to the driveshaft?

Hey there, on the one that I made I made a plate to bolt to the top of the lower unit via the same bolt patern and board a hole for the output shaft. I made a bearing holder for a sealed bearing to fit the shaft to help with side pressure because mine is chain driven from the motor. Then some uprights for the motor to bolt to (slotted to tension the chain) and a #35 chain to drive it. As far as forward and reverse the merc lower unit is simple, a rod in the front from the factory with a lever extention works great,THANKS.

 

[wbeaton]

Re: Homemade outboard

Hey there, on the one that I made I made a plate to bolt to the top of the lower unit via the same bolt patern and board a hole for the output shaft. I made a bearing holder for a sealed bearing to fit the shaft to help with side pressure because mine is chain driven from the motor. Then some uprights for the motor to bolt to (slotted to tension the chain) and a #35 chain to drive it. As far as forward and reverse the merc lower unit is simple, a rod in the front from the factory with a lever extention works great,THANKS.

Chaindrive. Interesting. I was thinking of running direct from the crankshaft to the driveshaft. I have several old 5.5 - 7.5 hp midsections with full shift lower units I could adapt to it.

This might be a fun winter project. I'll give it some more thought.

 

[maxum247]

Re: Homemade outboard

Yes, I got my test done. It did work pretty well as far as forward and reverse, but the prop is a little bit to much for the motor. It would only go ( I'm guessing) about 10 mph, but it is a 35hp lower unit. I'm thinking maby a 10hp lower end would be more sufice for the little 8 hp briggs. It's too much water for the little guy to push, but I was happy because it did work. THANKS.

The speed sounds about right for the 8. You may get a couple more mph with a smaller h.p. lower unit by minimizing drag and raising the rpm. I'd guess a lower unit in the 6 to 15 h.p. range would work well. But remember the prop won't ever turn the rpm it did with the outboard powerhead, the rpm of the aircool is far less than that of the outboard.

Good luck! Fun tinkering on these things ain't it?

max!

 

[rtpassini]

Re: Homemade outboard

i have a spare r1 motor that i want to rebuild and put on a boat...150 hp at 11,000 rpms would be FUN!

 

[Rancherlee]

Re: Homemade outboard

i have a spare r1 motor that i want to rebuild and put on a boat...150 hp at 11,000 rpms would be FUN!

why not, yamaha already uses versions of the R1 engine in a snowmobile and a wave runner.