Re: 93 Volvo-Penta 434A 4.3L won't start.
Time to work your way back from the coil the main harness connector.
Check to see if you have power to the automatic choke coil with the ignition in the run position.
Does your boat have a kill switch with a lanyard on it? Is it on, if it's on, is there power to both sides of it? If it goes bad, it kills the power to the ignition.