Milvina is in Germany for the winter, so I will be working there. The weight of American purchased cable is prohibitive for shipping.
One issue will be what I can get in Germany. Tinned wire is not widely seen as important in Europe.

Our starter is wired with welding cable, which is perfect after 10 years. Nice big cable with no measurable voltage drop over a 12 foot run each way. It is in a clean, non-oily environment, and we keep our biges dry. Ends are soldered and well sealed against water ingress.

I will definitely solder the terminals, as well as crimp. I realize that the American consensus is crimp, but the Euros are of the opposite view. At least as many Euro boats circumnavigate as American.

One question. When perusing the calculators for voltage drop on the web, I find that the calculated cable diameter for a 1 volt drop in 30 ft each way cable and 450 amps load varies from 10 mm (say 3/8") to 13 mm, say 9/16". Who is right?

The thurster motor is 5 kW at 11 volts, which equals 450 amps. The equipment is sold with a 500 amp fuse. I wonder how often the full current will flow.

Like Brian Woloshin (refer to his comment) I am not enthusiastic about a battery forward in the sail locker. I also wonder about the drop in voltage when the recommended 100 AH starter battery runs a 5 kW motor. Our main house battery is 660 AH, so will not drop voltage so much, although of course it will see longer cable run than a battery beside the thruster.

Does anyone know how much resistance there is in a good bolted connection? The losses in each termination wil be equal, whether the cable run is short or long.