I own a few vintage Mercs. I pulled the lower unit off on in order to change the waterpump impeller, and was amazed at how little friction there was when I turned the driveshaft by hand. Granted, there was no load on the output shaft.
I put the new impeller in place, and the effort to turn the shaft went was so much greater that I could hardly turn the shaft at all.
I would expect that by removing the waterpump impeller, and maybe the reverse gearing, you would be fine using the existing lower unit.
-Tom
--- 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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