My guess would be you have a single
problem with the water sensor on the saildrive and you believe it's 2 alarms as the light bulb is bleeding over on the panel and it appears as both a saildrive alarm and an oil pressure alarm. I say this as everything is OK when you disconnect the saildrive water sensor.
A couple of tests you might try. With the saildrive water sensor disconnected (no alarm), ground the wire connect to the oil pressure switch. You should now have an oil pressure alarm. This will insure that the oil pressure alarm circuit to the panel is working. Remove the saildrive water sensor and see if there is water between the rubber seals
, if no, replace the sensor, if yes, haul the boat and fix the seal.
This is straight forward troubleshooting.