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Re: Homemade outboard motor using briggs 2hp

68.4.213.15

Posted by machnumber2 on February 28, 2003 at 21:55:55

In Reply to: Re: Homemade outboard motor using briggs 2hp posted by KenOhki on February 28, 2003 at 19:32:12:

Hi,
That is a great idea and would definitely work. Its like an o-ring type seal only wider like 20 o-seals in a row. Regarding the clamps I would double up at each end on the rubber shaft area. I would do this out of concern that the clamp would not apply totally even pressure all around the circumference, I assume just under the screwhead of the clamp the pressure ( or tension) might be less then at the rest of the areas, so I would put one hose clamp with screw at top then another right after that with screw at bottom then ditto at the other end. This is just my assumption on hose clamps, its probable that they do provide even pressure throughout. We have to make sure that the lubricant does not eat rubber. I have tossed so many ideas in my head about how to keep the water out but they were all variations on the same thing, trying to make a conventional stuffing box, your idea is original and elegant I like it. For my project I finally gave up and bought a conventional stuffing box that would fit a 5/8" shaft, it cost $30 at the shipyard, and is missing the jam nut but I was pleasantly suprised I was expecting to pay more. Since I have it, I am going to play it safe and use that. I was thinking about your idea about the flexible shaft. It solves a ton of problems at the outboard lower end. The concerns I have about it are: 1. I would have to find a flexible shaft or search for a used weedeater or similar. 2. I would probably have to make it a direct drive onto the motor. Since the briggs turns at 2000-4000 rpm and my prop's max design rpm is 1400, I must have a way to vary the engine/prop rpm. So if I used a flex shaft I would have to hook it up it to gears or pulleys to do that and that would complicate things. 3. I am concerned that the flex shaft will be able to handle the torque of a 2hp engine, and in the future if this things works I want to put a 5 hp on this lower end. My original idea was to use a vertical crankshaft engine and attach a vertical shaft directly to the output crank, send it down to the lower end where it connects to a right angle bevel gear drive where it does two things - reduces the shaft rpm compared to the engine rpm and also of course takes a vertical spinning shaft and converts it to a horizontal spinning shaft. I could not find any right angle gear that was less than $200, and the ones that I did find were like for some heavy industrial use. Nor could I think of any old appliance or junk that uses a right angle drive that I could scavage. I gave up on that Idea and decided to go with belt drive. The belt drive allowed me to simply use varying size pulleys to vary the engine/prop rpm ratio. I expect that if/when I get this thing built, the prop RPM will not be correct and I will have to trial and error different pulley sizes to achieve the perfect rpm so that the engine power is used most effectively, so that there is not cavitation or other problems..., the pulleys allow me to do that easily. I could also use an idler pulley between the drive and driven pulley to act as a clutch that I could have both neutral and forward speed. I then got greedy and wanted reverse. I started searching for a simple gearbox that have forward/reverse on the internet but again the ones I found are for industrial use and very expensive and I could not think of where to scavenge one so I gave up on that. My goal here is to make this thing work so that I can put it on a skiff to cruise the harbors here in southern California with my wife. It would be great if I could watch this old motor live again and be useful.

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