Oil Pressure and Water Temp alarms for Port and Starboard Engines. 1 Light for each and the rotary switch can test if it still works. The two switches turn the alarms on. Your wiring diagrams should call out wire numbers on engines. For my 78 the oil pressure sensors are on a 3 sensor tree towards the back of the engine (one for the alarm, one for the gages, and one to operate hour meters) and the water temp switch is at the forward end of the upper water manifold. A few years back, Sams had readable replacement plates but I may have gotten one of the last good ones.