electrical panel questions

I was looking in my electricla panel last night, in teh 70 53MY the electical panel is in the port engine room and have a couple of questions...

- on the wall inside the panel, I have 3 black donut shape devices, marked transformers... 2 near the top, one a tthe bottom. they appear to be original, each has 2 or 3 wires but also one of the main 110v line looping thru. what are these for, don't see any reference to there in the electical diagrams?

- next to the panel, I have a external rotary switch. all the shore power lines appear to be going thru there, has 2 off and 2 On positions. I 'think" this is to switch the shore power inlets between port/stbd... is it? not sure if it's original, the diagrams show a selector switch but different...

- on the hull, next to the panel, I have 3 large fuse holders, empty... appear original... what were they for? someone mentioned fuses for the battery feeds to the selector switch but it doesn't seem like that's what these are for. the wiring to the back of the port/stbd switch on the panel appear original and goes straight down in the bundle going to the genset room where the batteries are.

thanks for any clue!

pascal
1970 53MY

Hi Pascal,

I have a 53' 1972 MY, the only panel such as you describe on my boat is the battery charger, which has the the transformers you describe. If it's not the charger, it may be an isolation transformer used to prevent shore power vs on boat polarity and gd issues.
Mike - 53MY "Finally"

The donuts are for the ampmeters or in the older boats the watt meters. The three fuses were for the shore power mains. A lot of these were replaced with breakers.
Dave