Re: 4.3L V6 Mercruiser engine clicks when trying to start
Bad solenoid, slave solenoid, starter, or not enough power to the starter motor. Or flooded or frozen motor.
When did it last run? Anything unusal happen?
Yank your plugs to release the pressure, and see if it'll crank.
You can jumper both the solenoid right on the starter, and the slave (if you have one), to test those.