wrote:
I want to put a motor on an 8' inflatable dinghy. A big question is
whether I should use a conventional gasoline/oil based motor or go with
electric. The situation is as follows: I plan to take the boat out to a
complete wilderness (in a car/SUV) and use it there for, say, a week to
explore lakes and streams.

Why not get a canoe & paddle? Or a boat which can be rowed?
Likely to be almost as fast as a small outboard motor, or
electric motor, much more reliable, good healthy exercise.


... how do I recharge the battery/batteries if I decide
to go with electric motor? Is it possible to do it through the running
car in some way?

Sure, you could just connect the batteries to your car's
start battery with jumper cables. It might take a couple
hours of running at RPM above idle to recharge though.


... Is this a realistic approach anyway? Solar
power(likely, unrealistic)/other alternatives?

That depends on what the math of battery life vs recharge
times, and the speed/range of your chosen motor with the
numbers you get.

Years ago, I went fishing and frog gigging regularly with a
neighbor of mine who used an electric trolling motor on a
small (10' or so) aluminum jon boat. We went ten miles or so
on a plain old car battery, but then we could take a few
days to get it charged again vie household 120VAC current.
And went noticably slower at the end of the trip than at the
beginning.

... I would not have asked
unless electric motor was not so nicely quiet and environmentally
friendly and thus appeal to me. Using electric motor has its value, but
it is not clear if it holds it in the above set up.


Richard J Kinch wrote:
Easy to calculate running times for any given trolling motor and battery
combination. Now calculate or observe your hull speed. Now you know your
best possible range. Derate that for possible problems.


Also remember you don't want to run the motor at over 3/4
throttle for best range. I don't think hull speed will be an
issue.


My bet is a battery does not store enough energy to do what you want. The
energy density of a lead storage battery vs gasoline is ludicrous.


True but the battery does offer some advantages. It's quiet
and you can place the weight of it anywhere in the boat you
want.

Think of that 50-pound trolling battery as a gas tank that holds (the
equivalent energy of) a pint of fuel, takes all day to "fill" (recharge),
costs $$$, and wears out in a few years.

That seems rather pessimistic. A plain old lead-acid battery
can easily run thousands of charge-discharge cycles if it's
treated properly. And the power equivalent is much more than
a pint of gasoline, especially if you factor in the woeful
inefficiency of internal combustion engines.

Fresh Breezes- Doug King