How do I set up the distributor to get the correct firing order for the 120 MerCruiser?

To set up the distributor for the 120 MerCruiser, first ensure the engine is at top dead center (TDC) on the compression stroke for cylinder number one. Next, align the rotor to point towards the number one spark plug terminal on the distributor cap. Then, follow the firing order (1-3-4-2) and connect the spark plug wires in the correct sequence around the cap. Finally, double-check the connections and ensure the distributor is securely fastened before starting the engine.