I have a 38 Lightning with 575's. Right now the switch for my Corsa Captains Call exhaust pulls power from the docking light
switch right beside it on the panel. If I have the switch on the closed (quiet) position and shut the engines off power is still being drained from the batteries and it doesn't take long before I need a boost. I know that if I just flick the switch to open there is no battery drain but I don't always remember. I also know that I should be manually turning the battery switches to the off position but once again I don't always remember.
I would like to pull the power for the switch from an ignition
switch source so that if the key is off so is the power. Is there a way to wire it so that if either engine key is on power is still going to the switch? I do have an auxillary fuse panel under the dash but it is not controlled by the ignition switch being in the on position. Thanks for any advice.

If the Corsa System was installed at the factory, then it should have a weatherpack harness of it's own that plugs into the engine harness. Corsa made it's own little harness that came with the kit.

That being said, if you bump around under the helm somewhere on your fountain there should be at least one power location that is tied to keyed ignition. If not, you can tap 12volts from the bilge but be very careful where you get power and how you connect it. Use heat shrink connections etc... Completely disconnect any/all the batteries while working.

I used to have that system. Nice, works well but downside is it does burn power continuously while in closed mode and running. However, you are doing the right thing by making sure it's ignition activated. That's how it really should be. You'll hear the clunk when you turn the key on in closed mode.

Also, that power source typically has an inline fuse as well. I think around 15-20 amp fuse...