G'day Orfish, All.
At 01:02 PM 28/11/2010, orfish wrote:
>Newbee so dont forget we laugh together right? Ok my idea for my 34
>foot chb is to gut the 8hp gas outboard motor stuff in a 1/4 hp
>electric. Then power the new electric outboard wiit with a 5 kw
>northern lights generator. Would this work? Thoughts very welcome.
Okey dokey... Firstly you'd want about 3hp or so electric to replace
that 8hp gasoline dinosaur, just looking at a performance point of
view. In my 11' (3.3meter) plywood skiff I have a 48-volt set of 90
amp-hour lead-acid batteries that gives me an hour at about 1.5kW
(not that I've done an hour at full throttle yet). I'd much prefer to
be using Lithium batteries for lighter weight and more available
energy, but the cost/benefit isn't there for me. My outboard is a
converted 4.5hp outboard, with a DC motor, controller, cooling fan
and contactors, some photos can be found at:
http://jcmassey.gallery.netspace.net.au/album05
Next, what sort of motor are you looking at? Talking about a
generator with nothing else makes me think you're looking to run
straight from the generator output to the motor, with no controller?
If you are going to do that, and are looking for your 3 mph trolling
speed, you could use pretty much a wide range of outboard sizes, with
a largish prop for quieter trolling, but then you have a noisy
generator, so you're loosing the quietness. A 4-pole motor will run
at about 1700RPM, 2-pole motor at twice that, 8-pole motor at half
that, so if you really wanted to use a direct connect generator-motor
combination you could, but:
* it would use more fuel than an equivalent performance outboard
* it would make more noise than an equivalent performance outboard
* it would be less controllable than an equivalent performance outboard
If you ask my opinion (getting it anyway!) I'd use a set-up like mine
with batteries and a DC motor (or brushless DC), controller, etc.,
and use your main engine when your batteries go flat (possibly with a
48V alternator from the main engine as alternative to "mains" recharging.
But you will get lots of opinions.
Regards
[Technik] James
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