My neighbor has a 2001, 75hp, carbureted, four stroke Mercury outboard
(75ELPT, SN OT395139).

It idles a bit rough but runs great at full throttle and everywhere in
between.

When looking at it, I noticed that the two electric fuel enrichner solenoids
(chokes) were very hot when I touched them. I checked them with a voltmeter
and both were still energized at 13.5 volts even after the motor had been
running for 20 minutes. What is keeping them energized?

Are these enrichners activated by pressing in the ignition key like my old
Merc motor was, or are they controlled by temperature or what? Thanks.