How do you set the timing on a 305 Chevy marine motor?

To set the timing on a 305 Chevy marine motor, first, ensure the engine is at operating temperature and turned off. Disconnect the timing connector to bypass the electronic control module, then use a timing light to check the timing mark on the harmonic balancer against the timing tab on the engine. Adjust the distributor by loosening the hold-down bolt and turning it until the timing light indicates the desired timing setting, typically around 8-12 degrees BTDC for a marine application. Finally, reconnect the timing connector and recheck the timing to ensure it remains accurate.