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I think you need the power reserve in case the wind comes up.

Also, the safest route prop-wise is to stick to what is already there.

I think a pair of HPEVS AC-9's could be the ticket.
Yes for power reserve!

old prop can be a start when you don't know your motor characteristics, then adjust until right.

old prop usually means you need a big rpm reduction (you'll need that anyway in most situations).
 

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I am nearly their with my conversion, my old forklift motor is mated to the propshaft batteries and controller mounted and cabled up. This week its other wiring and and a test run hopefully.
My boat is 57 x 12 and weighs over thirty tons and I am happy cruising the inland waterways at 3 -4 mph. Charging is taken care of by 3.6 kw of solar on the roof.
In the end I suspect I will be fine tuning the propeller, but you never know it might be right:eek:
What kind of reduction gear do you use?
 

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Its direct the original diesel worked through a 2 to 1 gearbox, the top revs were 3100, the electric motor I have chosen has a 1680 rpm at 48 volts.
I have used a 60 volt system but dont expect to get anymore rpm,and to be honest dont want to do the 7 - 8 mph this achieves anyway.
Be carefull when testing, you -do- need a reduction gear, don't burn out your motor!
 

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Oh no! It is a series motor which I understood to have lots of torque at low rpm so thought it would be ok. I will monitor the temp of it whilst on test to see how it performs
yes that's good for a car, on a boat it doesnt matter you want continuous power in a boat, and if you turn too slow you don't have enough power.

Higher voltage = higher RPM

what controller do you use?
 

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I would speculate that the motor controller would overheat and shut itself down long before the forklift motor would be hot at those amperages. I'm interested to hear how your first test went whenever it happens!
the motor needs RPM to cool itself (or external fan).

problem is at low RPM you need lot's of current to make power. high current = high losses = heat.

but 12 inch motor...that's a beast!!
 

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So Yesterday I had a trial run, it performs well draws 52 amps 3.3KW at approx 3mph, the temp of the motor was 72 degrees C at the end of an hour run, controller was 32 degrees.
are you measuring motor amps or battery amps?
did you measure RPM?
dit you measure motor voltage (should be pretty linear to RPM)

it sounds like it's working well! 72 degrees C was measured on the outside or the rotor / stator windings? I bet you could smell the motor ;)

1/ should I fit the 400 amp breaker or leave it at 300 amps?
2/ should I test it without the breaker to see what the motor really does draw at speed?

3/ Is 72 degrees to hot after an hour or is it normal? will running cooler help performance and life of the motor
cooler is better, try the fan. this also depends on how the motor is mounted (free flow of air or restricted)

I like to be able to draw full power for a short period, maneuvering (stopping!) needs power. you could make some 'spring return' on the throttle lever so it doesn't stick to full power.

Check the controller specs on continuous power rating.
 
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