Interesting event today. My boat died. I was towing kids around the lake.
I stopped, turned off the motor, turned off the blower. A minute later I
turned on the blower. I turned the ignition key. The oil pressure alarm
activated. I turned the key to start. Suddenly dead silence. No
electricity. (Prop was down. How do you raise a prop when the electricity
is gone?) I/O Mercruiser Alpha One 4.3L 6Cyl efi. 2005 Sea Ray 185

Flagged a good samaritan down who towed us a short distance back to our
boat-in camp.

I checked my battery connections. Solid. No electricity.
I pushed the red breaker reset button on my motor. No electricity.
I swapped all my under dash fuses. No electricity.
I checked my drive oil level (I was out of ideas). Still visible in the
reservoir, but slightly below the add line.
I pushed the red breaker reset button a couple of more times just for fun.
My son tried the blower. Electricity!
Used the boat the rest of the day without any problems.

So, what happened?