Dunno, I've not done that but how hot was it? My guess is it was fine cos when I've changed the drive lub (often) it's never been anything more than a wee bit darkened. Maybe you were charged up and grounded youself to the drive... You'll be wearing them old purple nylon knickers again.
You've just reminded me so a wee note for you. The engine block of the KAD is not connected to battery negative but it is connected to the sea via a small cable on the inside of the transom shield. When you stop the engine, a relay pulls in to make a ground connection for the stop solenoid to activate.