Naked Science Forum

Non Life Sciences => Technology => Topic started by: peppercorn on 02/03/2010 12:15:16

Title: Are outboard engines lighter than other motors?
Post by: peppercorn on 02/03/2010 12:15:16
If I wanted a lightweight engine with only a dozen horsepower or so, running fixed high rpm, would a 2nd hand outboard be a good bet?
Title: Re: Are outboard engines lighter than other motors?
Post by: graham.d on 02/03/2010 13:03:22
You can buy small engines as part of a generator or pump or (probably) for general use. An outboard is very specific to turning a propellor sitting in water so you would have bits you don't need and a rather inconvenient modification to get the rotary power out and into whatever you want to drive. Even a lawnmower engine would be more convenient I think.
Title: Re: Are outboard engines lighter than other motors?
Post by: peppercorn on 02/03/2010 13:07:10
What if lightness is key though?  I also think a o/p shaft speed from a outboard would be a good match for the large alternator I have in mind.
Title: Re: Are outboard engines lighter than other motors?
Post by: graham.d on 02/03/2010 13:29:43
I don't know whether outboards are in lighter than a general purpose engine but I doubt it, and it would not be very convenient to modify. Try Briggs and Stratton, Honda or any of the numerous small, general purpose engine manufacurers. Some outboards are VERY heavy by the way and, I can confirm, even the lightest are not that easy to lower from a boat onto a dinghy :-)
Title: Re: Are outboard engines lighter than other motors?
Post by: LeeE on 02/03/2010 13:59:22
I think the only concession to lightness in outboard motors are that they're capable of being lifted and carried (but not that it should necessarily be easy to do so, otherwise they'd all be pinched).

I'd suggest instead, that you look at the small IC motors fitted to hand-held power tools, such as strimmers, for very low power, or chain-saws if you need something a bit beefier.  Your cheapest option may be to use a 49cc moped engine from a breaker's yard though (and I'd imagine that they're probably designed for longer running times than a typical power tool motor).
Title: Re: Are outboard engines lighter than other motors?
Post by: Karsten on 03/03/2010 21:52:20
Outboard motors also rely on water-cooling. Old lawnmower motor might be another option. Simple, light, air-cooled.

Here is a generator built with a lawnmower:
http://www.webpal.org/b_recovery/3_alternate_energy/electricity/lawnmower/generator/generator.htm
Title: Re: Are outboard engines lighter than other motors?
Post by: syhprum on 12/10/2017 18:13:52
I would not recommend a moped motor they had contact breaker ignition that requires maintenance whereas a lawn mower engine would have electronic ignition and a recoil starter, I recently had to scrap my 25 year old Flymo as parts where unobtainable and it broke my heart to dump the engine that was still running fine
Title: Re: Are outboard engines lighter than other motors?
Post by: chris on 13/10/2017 07:50:39
I would not recommend a moped motor they had contact breaker ignition that requires maintenance whereas a lawn mower engine would have electronic ignition and a recoil starter, I recently had to scrap my 25 year old Flymo as parts where unobtainable and it broke my heart to dump the engine that was still running fine

Completely agree. I don't buy Mountfield mowers any more, because these days the quality of the bodywork is so poor that the engine is barely run-in before the mower chassis is rotting through. We're pretty diligent about cleaning up our machinery after use, but even then it still falls to pieces. Contrast this with the first generation of mowers we had that were still in one piece after 25 years but eventually suffered the Flymo problem highlighted by @syhprum

"They don't make things like they used to..."