i havent priced a 30lb, but off the top of my head, a no name made in china
13lb trolling motor is about AU$200 while a 50lb is about AU$500. add in
battery, wiring etc and i could buy a brand new petrol outboard for those
prices. I think the electric outboards are still really expensive in
australia for what they are. they will probably come down in price in a
year or two but for now i'd feel a bit cheated paying for one.

Shaun


Should also have mentioned that my 30 lb Endura pushes a 14' Hobie at
about 3.5 mph in still water.

BS

Shaun Van Poecke wrote:
i havent priced a 30lb, but off the top of my head, a no name made in china
13lb trolling motor is about AU$200 while a 50lb is about AU$500. add in
battery, wiring etc and i could buy a brand new petrol outboard for those
prices. I think the electric outboards are still really expensive in
australia for what they are. they will probably come down in price in a
year or two but for now i'd feel a bit cheated paying for one.

Shaun

Should also have mentioned that my 30 lb Endura pushes a 14' Hobie at
about 3.5 mph in still water.

BS


That does seem rather high. My 30 lb was $99 and the 50 Lb $130. But
they work really well, appear to be well made, and are very reliable.

BS

On Sun, 11 Feb 2007 07:33:28 -0800, R Swarts
wrote:


Should also have mentioned that my 30 lb Endura pushes a 14' Hobie at
about 3.5 mph in still water.

BS

It's always the maker's claimed thrust that raises questions in my
mind. They take the thrust reading stationary, as far as I know.

Anyway: if you maintained 30 lb thrust at 3.4 MPH
that would need 203 watts or more
i.e. 17 amps at 12 volts
to provide about 0.27 HP.

Brian Whatcott Altus OK

Brian Whatcott wrote:
On Sun, 11 Feb 2007 07:33:28 -0800, R Swarts
wrote:


Should also have mentioned that my 30 lb Endura pushes a 14' Hobie at
about 3.5 mph in still water.

BS

It's always the maker's claimed thrust that raises questions in my
mind. They take the thrust reading stationary, as far as I know.

Anyway: if you maintained 30 lb thrust at 3.4 MPH
that would need 203 watts or more
i.e. 17 amps at 12 volts
to provide about 0.27 HP.

Brian Whatcott Altus OK

Yup, that's right. And the motor actually consumes about 30 amps or 360
watts. So if we believe the manufacturers specs in this case it gives an
efficiency of about 56%. The 50% number appears to be about right for
most trolling motors I've run across. Of course the motor is more
efficient, but that number includes the prop efficiency.

BS

Jet boats are not particularly efficient and are used in shallow water
because outdrives tend to come apart when they hit a rock. They are good on
rivers but not on open water.

your trolling motor will probably be less than a battery bank to run a bilge
pump and remember that it is not just volume that comes through but also you
want velocitiy at the outlet of the jet.

Brian

Shaun Van Poecke wrote:
ok, Ive heard this idea brought up before and seen it poo poo'd, but can it
work to some extent?

Ive got a 14' cat that i store next to the beach in sydney harbour and i
like to get out for a sail when i can. Unlike most cats this size, it has
heaps of flotation - 3-4 adults and still not sinking anywhere near as much
as a hobie 14 with 2 POB. It has an outboard bracket on the back which was
on it from the factory, but i've destroyed 2 admittedly cheap and nasty
second hand outboards on it so far. I have a new honda 2hp 4 stroke on my
dinghy that i dont want to put on the cat because it would probably suffer a
similar fate.

What happens is that because your moving so fast, the outboard gets
completely drowned, as do the people sailing for that matter ;-) an
outboard might work on a lake or something, but sydney harbour gets choppy.
The thing is, this boat was designed for island hopping the whitsundays and
the manufacturer claims enough flotation for 4 people, plus camping gear, a
stove, and food and water for a week! I cant see how they get the outboard
to survive...

i do ok if i get the outboard started and there are no waves and i just
motor round on it. a 2 or 3 is plenty to move along. its rated for a 5 at
maximum. the trouble is, as soon as you sail if there's a bit of chop, that
motor is getting a drink - then you'll never get it started. I want a bit
of propulsion for getting into some of the finnicky bay areas rather than
spending a couple of hours tacking to death, 5 minutes of propulsion would
get me there. propulsion would also be nice for getting back in if the wind
dies, and finally as a backup just in case something breaks. i like to go
out when the wind is big, and ive already had a couple of incidents with
snapping a gooseneck fitting, and destoying a couple of jib cleats.

so here's what im thinking; a 1250GPH bilge pump in each hull, intake hoses
going into the water, outlets hooked up to hoses facing rear. these draw 5A
each and are cheap to buy. A 40-50AH sealed gel cell would give me a lot
more power than i need. I cant see myself using ot for longer than about 30
minutes to an hour at a time. Is this going to move me at all? at least
more than trying to paddle the boat by myself (which gets me almost
nowhere!) would i get any benefit from using smaller diameter hoses to
create a stronget 'jet', or am i just unnecessarily loading the pump for no
real gain? am i miles off in the GPH stakes.... do i need a lot more
pumping to get any effect?

im not looking for a speed boat here, just *movement* even 1 knot would be
something. benefits to this system are that its fully submersible,
completely unobtrusive, almost silent, would cost me about $100, starts
instantly when i need it.

thanks,
Shaun


Much bigger than what you all are talking about, but this is electric
propulsion done right:

http://www.asmomarine.com/2005/asmo_uk/00.shtml

There are a number of others selling electically propelled boats too.
Just google up electric boat

BS