Can someone confirm the charge lamp is suppose to be lit if everything is working correctly when the engine is running? The manuals have some conflicting info regarding if the normal state should be on or off. I have the Yanmar 2GM, instrument panel type B.

Is there an easy way to check that the alternator is working?

Lamp should be on when key switch is on but engine not running. Once the engine starts and alternator is producing output the lamp should go out. If the lamp stays on after starting, the charging system is not operating properly.

Thanks, I was able to confirm today that's correct. My alternator was not working, I replaced it and the lamp now goes out once the engine is running.