Circuit Breaker labeled APS?

PCP ? I would be guessing rite now.
You found the Cat version of a Mathers box.

Powertrain Control Processor is what PCP stands for.

Not that I ever heard about that before, mind.
But your photos made me curious, and since I'm right now coming back from Alaska on a 145k GT vessel, and I have no duties whatsoever apart from eating and drinking like there's no tomorrow, I googled a bit for those bits of kit in your photo.
And what I found confirmed, yet again, that every day is a school day.
In fact, essentially the setup you've got is exactly what I defined "mental" in my post #52, i.e. mechanical levers directly connected to mechanical gearboxes (though this isn't actually clear from your photos, but it's a reasonably safe bet), and connected also to a rotary sensor which converts the levers position into an electronic signal that in turn controls the electronic governor on the Cats.

Don't be concerned about my rather harsh definition, anyway.
That was only triggered by the fact that I've seen quite a few C12 powered boats, with several different control levers (ZF, Kobelt, Glendinning), and all of them, bar none, had electronic levers connected by wire to the engines, with a mechanical actuator for the gearbox if and when it didn't have an electronic solenoid actuator.
And it seems to me that this solution I'm much more familiar with is a more elegant way to skin this particular cat, compared to the other way round.
But what do I know? If Egg Harbor decided to go for that installation, they must have had their reasons.

Anyway, I'm attaching the documentation I found, which brought me to the above conclusion.
I'm afraid I can't help you further though, because as I said it's a setup I never came across before, about which I know nothing at all.
And frankly, I'd rather go back to my eating and drinking duties now, than studying Cat manuals in detail...
Good luck with the reading!

PS: sorry, I just noticed that the Cat manual exceeds the forum size limit for attachments, so I just extracted a couple of pages to give an idea.
If you (or anyone else interested) PM me your email, I'll sent you the full document.

Brother, What the Frak are you doing partying on an Alaska barge and did not call me,, Frak Me.
(Reduced acronyms by request).
Please open another thread or at least a note, why your up there in the upper left coast, on such a well stocked little 145GT bote and not home in the warm Med..

Sorry for not having thought to give you a shout, but it's my boss who arranged everything.
And it was a bit of an afterthought also for her, who managed to squeeze the cruise within several weeks spent in CA/OR/WA.
I'll try in the next days to write a bit more about the trip up to AK, which I must admit was rather interesting, in spite of my strong preference for boating that doesn't involve thousands of other people around you...!

In the meantime, how's this for an appetizer?
Taken just half an hour ago while approaching Puget Sound, for disembarking tomorrow morning in Seattle...

Funny you bring this up this morning. North Florida got a treat last night.

Wow, that must be pretty rare in FL.
Even up in the northernmost point of your State, you are still at the latitude of the southernmost point of the Med, which is in Africa!

Yep, very rare.
Were around 29.34 N .

BTW, just in case you misunderstood, 'twas a 145 thousands GT cruise ship.
Not my favourite type of boating, but while going around Glacier Bay I must admit that I didn't regret not being there with my small tub!

Yep, A lil cruise ship, Probably the Sky.
Still way to many people (more than 2) around.