No Power In Tinnie - Isolator To Blame?

[Panther]

I recently got back from a forgettable boating venture to the southern part of Bribie island in the passage where we encountered head on 28-32 knot SE winds on the way back to the ramp. Also the wind and run-out tide were in opposing directions. Very choppy!
 

Took the best part of an hour to get back and all on board got suitably soaked - I have a 4.3m stessco side console. Great to test the boat in those conditions but don’t need to do it again! Plenty of spray came overboard.

Anyway, once home, I cleaned the boat as usual and tilted (electric) the motor down to run the freshwater through - all standard stuff. Also as per normal I keep the motor down till the following afternoon when I tilt it back up. But this time there was no power - no electrics working in the boat at all?
 

I checked the battery and the view-hole looked black so tried charging it overnight. Still black and still no power to the boat so put it down to a dead battery... Bought a brand new battery and same electrical issue. Checked first fuse in line and looks fine.

I figured the next component is the isolator switch with the standard exposed red plastic key on one side and the wiring hidden on the other. When I took out the red key I noticed a small drop of water on the end. I wiped it off, reinserted and got more moisture...

Could moisture in the isolator be causing the issue? Is this somewhat common for tinnies after a rough day.... hoping someone has more knowledge on this as taking out the isolator looks fiddly. I want to avoid if possible!
 

Thanks.

[aussie123]

Generally water will not worry them if wet from the key side so you need to grab a multi meter and check the voltages on the back of the isolator switch to see if it has been damaged with water.

First check the terminal that is connected to the battery and if you have full power to the switch, turn it on and check the other terminal to see if power is getting through the isolator.

If you have power on both lugs of the isolator when turned on, you need to check any buss bar connections, circuit breakers and fuses on the main power feed cables.

Also look for any burnt wiring that may have shorted from the water.