Absolutely.
And the common boat has a prop and drive system that is very ineffcient.
The desirable thing to do would be to go to a prop 2-3 sizes large than
commonly used.
The problem is you would need to change the driveshaft as well, as an
efficient prop wont fit in the standard aperture.
As such, this is almost never done.
Also, large props are expensive.
In normal boats (inboards) you have gearboxes that requite cooling, and
large hot oil and hydraulic coolers.
All the heat is inefficiency (as is all noise).
Heat does not appear from zero - work and then friction creates it. All
heat created is a loss vs. having that energy go to the prop.
The driveline wastes about 1/3 the energy.
The prop wastes about 1/3 to 2/3 the energy. Normal props are very
inffefficient at most speeds.
So, only about 1/6 of the energy actually goes to move the boat !
This is illustrated by numerous conversions done with small engines, and
or large props, where relatively tiny engines move relatively very big
boats.
On 11/09/2014 02:33, John Acord jcacord@gmail.com [electricboats] wrote:
> From reading various sources it seemed that a larger prop turning
> slower would give a more efficient transfer of the power.
>
> Also, I have heard that running the motors at lower rpm under load
> results in undesirable heating, thus the choice of a higher gear ratio.
>
> I found a listing in the Michigan Propeller catalog showing that there
> are some Evinrude & Johnson outboards with 2.42:1 gears. Since I am
> starting from scratch, not having an existing outboard in hand,
> thought I might look for one of those.
>
> thanks,
> John
--
-hanermo (cnc designs)
Posted by: Hannu Venermo <gcode.fi@gmail.com>
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