My '84 E-28 came with only the manual diaphragm pump in the cockpit.
I added a small electric bilge pump (I forget the brand) with an integral float switch. My bilge cavities are so small that fitting in both a pump and a separate switch would have been near impossible.
The pump has three leads, manual, automatic, and the neutral. I did not want to cut into the paneling on the side of my electrical panel so I used circuit breakers already there.
In my boat, on the back of the panel there is a copper strip running along the back of the breakers. This is the common "hot" connection to each breaker. I bent back and secured this strip to disconnect it from the bottom three breakers, Bilge, Stove, and Spare. On my boat, none of these breakers were used or connected to anything.
I then ran a wire from the common "hot" connection from battery 1 of the battery selector switch directly to the Stove breaker (with an in-line fuse to protect the circuit), and then a jumper to the Bilge breaker. While I was in there I also ran a jumper from one of the hot sides of the other breakers to a spare and used this breaker to power a new cigarette lighter type outlet.
I connected the automatic wire from the pump to the Stove breaker and the manual wire to the Bilge breaker, then connected the neutral to the common neutral bus.
This way, even when I turn the battery selector to Off these two breakers are powered from Battery #1. When I leave the boat I leave the Stove breaker closed so the pump operates on automatic while I'm away. When I get on the boat I press the Bilge breaker to pump out the usual accumulation. This is a lot easier than the old days when I had to pump the manual pump everytime I went out for a sail.
If the automatic pump ever has to run for an extended time while I'm away or the float switch gets stuck, it will drain down Battery #1 but I'll still have Battery #2 for starting (assuming she's not sitting on the bottom).
Words of caution. If you wire one of the leads directly to Battery #1 make sure you wire both to Battery #1. I thought about connecting the manual breaker to the common breaker bus but realized that if you do so you can make the bilge pump wires the only connection between Battery #1 and Battery #2. If the batteries have uneven charge and voltage, a lot of current can try and flow through these wires, blowing the fuse.
I haven't yet got around to making lables for these but will look for and engraver who can make those little black with white lettering things. Hopefully thin enough so I can just unscrew the ring on the outside, slip the lable under and screw back on. I hate cutting into or otherwise modifying panels like this.
Also, I periodically still pump out with the manual pump to make sure it is OK and to make shure flapper valves don't start sticking.
As far as sea cocks, I always close all of my religiously when I close up the boat (but not usually for just a shore excursion in the middle of a trip). I also periodically pour a little head lube in sinks and ice box drains with the valve closed and leave it there to keep the valves from sticking.