if the hour meter gets 12v accessory power its clicking up time... most often they are wired in to a key accessory circuit.

OldSchool is 100% correct 12v hour meter vs computer logs

I drive my boat in reverse to make the hours go down!

Yeah, on old school it will keep ticking along if wired the way you have... I have 6 more hours on port than strb due to a failed fuel pump and long ass ride home....
I've seen some newer after market hour meters that read when an engine is running via vibration, but wasn't sure how that would work out on a boat. The computers know all, but since my boat didn't have an hour meter, I installed new ones when I put in new engines last winter. 100 hours in 1 season!

My hour meters are wired to the purple wire/key on. Any time the key is in the run position, the meter runs.

I use to hook up the hour meters to the charge lamp on the alternator. When the alternator start charging the hour meter runs...

Peter

It does on my Formula and it did on the Chaparral I owned previously.