Pete, that powered the mothership, they had and still have a gas outboard
for the dinghy
. OP is asking about powering the dinghy
If the OP is content with a speed of about 3kt an electric
trolling motor is probably the cheapest option.
I would get a 45lb thrust MinnKota with DigitalMaximizer. DM is a PWM controller for the motor. At anything less than full throttle it saves on energy consumption
compared to typical motor controllers.
Anything over 45lb thrust is probably not going to push the boat
any faster, speed will be limited by prop pitch
and by being RPM
limited due to motor voltage. If the boat
were really really heavy the extra power would help maintain speed despite the weight but it won’t help you go significantly faster.
You can eek out a little more speed by replacing the stock prop with a Kipawa prop. Stock props are optimized for acceleration and shedding weeds. The Kipawas are optimized for a bit more speed. Alternatively you can use less power to go the same speed.
I would mount a 75-100W solar
panel flat about 2-3’ above the motor. I’ve read posts by people indicating they’ve done that and the dinghy never needed charging
from the mothership.