Usually it is the engine reservoir a little low. Try popping the cowling and you can fill the reservoir.
If you are on the water here is another fix: Loosen the cap and run the engine at a little higher RPM than Idle. That puts crankcase pressure in the lower reservoir and fills the upper reservoir, without the restriction on the upper tank.
Then replace the upper cap securely.
The lower tank runs from crankcase pressure and the upper runs from the gear drive to the engine.
If you have a digital system since 2003 models wtih SC gauges, it could also be the lower oil level. Sicne BCB uses a sending unit on the oil tank and monitors the level on that set up.
If that doesn’t get it, then you have other issues on the alarm and it could be many things.
BCB
.
