I picked up a Marinetics A/C breaker panel that has main breakers and
5 branch breakers. It seems the company is no longer in business.
The Neutral side of the main breakers goes to a buss bar with 5
terminals for 5 branch circuits.
The Line side of the main breakers goes to a jumper that connects the
hot side of 4 out of 5 branch breakers. The one not connected, is
labeled "spare" on the front of the panel.

The questions I have a

Does anyone know why the spare breaker isn't connected to the Line
jumper?

Another question. There is a "on/ok" green pilot light, with a
"polarity test" momentary switch below it.

I havent installed the panel yet. Is the "on/ok" light supposed to be
on when the main breakers are on? What is supposed to happen if the
polarity is reversed? When are you supposed to push the "polarity
test" button, and what should happen if all is ok or not ok?

The old a/c system on the boat has an old breaker box and a polarity
alarm that goes off if polarity is reversed. Is this panel designed to
be used with an alarm?

Sure would be easier if I could call the company.

Thanks for any info.