To who else needs to know.
So typical, the fuse for the thruster was inside the electrical panel in the engine room. Like that a great place to hide it!
It has to be there, for safety reasons. The longer the length of an unprotected conductor, the greater the chance of fire if there is a short circuit or overload.
Understanding the rules can help you find these devices easily.
Except for engine cranking, ABYC requires the overcurrent device to be as close to the
source of current as possible according to the '7/40/72' inch rule. For un-enclosed wiring connected directly to a battery, it's seven inches. If the wiring is directly connected to the battery but is
'fully enclosed along it's entire length' for protection from accidental damage, the overcurrent device must be within 72 inches.
For thrusters, the wire normally comes from the main battery switch and in this case the overcurrent device must be
"as close as possible, but not more than 40 inches" from the switch. So...look for the battery switch and you will find the fuse within 40 inches, usually much closer, because the rule says "as close as possible".
In our MS390, it is right next to the main battery switch, maybe 10 inches downstream.