Yanmar SD20 - Testing the Seal Sensor Alarm

[Zoid]

I've got two Yanmar SD20 Saildrives on my catamaran and during some annual maintenance I noticed a warning label below the seacock that I hadn't seen before. It states "At start of every season Test Rubber Seal Switch: Remove Switch, connect warning buzzer and lamp: insert contact points into water: warning should occur". I've attached a picture as well.

I definitely want to ensure that the sensor works as it goes off when water has gotten past the first seal. That being said I assume the sensor is that white bit to the right of the label. It gives no instructions as to how to safely remove it.

Has anyone done this before? I assume I take that white piece out (somehow) and then with the engine running put it in water and see if the warning light goes off and if the alarm sounds.

Any suggestions?

[Zoid]

Forgot the picture...here it is

[ggray]

That's it, to the right of the label.

It just screws out with your fingers.