wrote:
On Wed, 16 Apr 2008 13:38:02 -0400, Martin Baxter
wrote:

wrote:
On Tue, 15 Apr 2008 18:36:10 +0200, "Edgar"
wrote:

"Martin Baxter" wrote in message
...
Don't leave out the fact that the electric trolling motor power is
produced directly at the prop. There is significant power loss in a
gas outboard between where it is produced and the prop that does the
work.
Hmm, I don't really know, but I don't think the losses should be all that
big, one little water pump to turn, on set of crown and pinion gears.
Intuitively I don't think you'd lose more than 15%..

I'll bet that most outboard manufactures measure output of just the head,
no shaft, no water pump.
It would not be as much as that. 3-5% would be about the right amount.
I think you're right Edgar, on a slightly larger motor, but two horse is
pretty small and the losses would be more significant, frankly I'd be
surprised though if they were more than 10%

I think it would be a bit more than that. The drive train has to turn
a 90 degree corner. And don't forget the power consumed by the
alternator, along with the already mentioned water pump. These things
add up.


Alternator? On a two horse?,

Cheers
Marty


Suzuki DF4 and DF6 are both available with a 6 amp alternator

http://www.suzukimarine.com/sr_07/df6-4/features/

Ok, so twice the two horse, now the gear loss becomes less percentage
wise. Six amps, fourteen volts, is 84 watts, just a bit bigger than
1/10 hp, even at 80% efficiency, even if the alternator is actually
putting out the full six amps, still not not significant.

Cheers
Marty