Look into golf cart motors. Consider duty cycle and run times with respect
to motor choice and battery bank size. Larger engines can be found in the
fork truck industry. Both the golf cart and fork truck would provide speed
and direction controls as well as basic mounting design. Your small diesel
generator may need to run much longer than your motor and or you will
require dockside recharging and use the diesel as back and top-off while at
sea. Keeping the generator output close to the energy needs of the motor
will increase the overall efficiency of the system. It would be useless to
require 4 hours of charging to produce the energy needed for 15 minutes of
motoring unless the battery bank was large enough to carry reserve energy in
far excess of your typical needs. The primary charge would then come from
dockside sources and your generator would be always on stand by.

There is a lot of info on the net about hybrid electric craft. You just need
to apply the information to your specific application.




"Richard Casady" wrote in message
...
On Sat, 15 Dec 2007 09:50:00 +0100, Heikki wrote:

John C. wrote:

Run it as a generator and use it to charge an oversized bank of
batteries.
With an electric motor you will gain variable speed and direction
without
have an engineering nightmare.

I have been speculating about a diesel-electric propulsion for a smallish
sailboat. Does anyone have links to, or experience with, small electric
motors that are suitable for continuous use - most of my googling finds
bow
thrusters and other extra machinery.

There are electric fishing motors, in the one horsepower or less
class. Maybe enough power for an under twenty foot boat. Not good on a
windy day.

I am thinking of a fairly small engine, say 5-10 Hp, to be used mostly in
manouvering in and out of marinas, and occasionally coming home from a
calm
sea. Would it make sense to mount the whole engine on the transom-hung
rudder? That way it could turn with the rudder, and give good steering in
both directions. When not in use, it could be lifted out of the water, so
I
could use a decent size of propeller for it.

There is the tried and true outboard motor. Hanging stuff on the
rudder sounds like a poor approach to me. Not to mention ugly.

Would anyone care to shoot the idea down before I get too attached to it.

Shouldn't be too hard.

Casady