One, VERY important reason for going with a drive shaft and bevel gears is that it makes an easy forward/neutral/reverse gearbox.
While a chain might be less drag, it won't be when you add a gearbox for reversing, too. Of course we are only talking about IC engines.
There's no reason not to use chain drive on an electric. Also, it would lover the profile of the outboard casing, too. However, I'd go with a cog belt drive to reduce noise.
--- In electricboats@yahoogroups.com, Keith Jacko <nrixez@...> wrote:
>
> I'm curious if anyone has any thoughts about why there are few (if any?) chain driven outboards available. I'm specifically thinking of electric outboards, of course, but the question really could apply to conventional powerheads as well. The drive efficiency of a chain would almost certainly be higher than that of a drive shaft / gear box.
>
> The only thing that comes to mind immediately is that perhaps chain-drive would require an underwater profile of the outboard that had too much drag?
>
> Converting an existing outboard seems to currently be the only financially reasonable option for getting a 15+ hp motor. It irritates me to think about the parasitic losses associated with the conventional outboard drivetrain though.
>
> Aquawatt has some larger outboards. Not sure if they're available anywhere yet, but they certainly don't seem readily available in the USA. Even if they are and I don't know about it, the $12k price tag is a bit overwhelming for a 28-ish HP motor (comparable 4-stroke outboards are available for about $4k).
>
> -keith
>
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