This is a good site with a bit of everything Cruisenews.net you'll get the inboard outboard go down to electric drive.That will let you know you can use as many rpm's as a prop will make good.
--- In electricboats@
>
> G'day cloudmagnet, All
>
> At 02:49 AM 30/01/2010, cloudmagnet wrote:
> >In the Photo section, in the "Default Club Album", there is a photo
> >of an outboard motor conversion (top row, second from right) to
> >electric. Now, from what I've been able to determine, an outboard
> >engine turns over at anywhere from a few thousand RPM to as much as
> >5 or 6 thousand, while most electric motors top out at 2500 RPM or
> >so. Can someone tell me how this seeming disparity in input speed
> >equates to output? What electric motors would be appropriate for
> >this type of conversion? Thanks
>
> I don't know what motors you have been looking at, but 2500RPM is
> pretty low. My two outboards (1.5kW and 4kW) rev to about 4500RPM,
> most on-road electric cars rev to 4500 to 6000RPM for DC motors and
> 9000 to 12000RPM for AC motors.
>
> Forklifts and other similar vehicles are designed using low battery
> voltage and high loading to be unable to be over-revved under normal
> conditions, without active rev limiting. As such they use motors that
> are rated in the range of 1500 to 2800RPM, but they are only
> nameplate ratings - the ratings that the manufacturer put on them as
> a statement of performance under certain conditions that suit the
> application - these ratings are typically exta-ordinarily
> conservative over what the motor is capable of.
>
> DC motors that are very large are also low revving - but any that big
> are way too big for an outboard. A motor 9" (230mm) in diameter by
> 18" (450mm) long can do 5500RPM, most motors smaller than this can do
> at least these RPMs. How big an outboard are you after?
>
> Typically the rev range of a brushed DC motor is very similar to the
> rev range of an ICE, so are a good replacement.
>
> Hope this helps
>
> Regards
>
> [Technik] James
>
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