Low oil pressure switch that opens at 7psi. When closed, this switch causes the alarm / buzzer to sound on the engine panel until the engine starts and the correct oil pressure is achieved.
Applications include these engines and the boats that we are aware used these engines... There may be other combinations as well:
• M-12 (Catalina 25, Capri 26)
• M-2-12 (Catalina 25)
• M-320, (C-27, C-28, C-30)
• M-25 (Catalina 30, Catalina 34, Catalina 36)
• M-25XP (Catalina 28, Catalina 30, Catalina 34, Catalina 36)
• M-35 (Catalina 34, Catalina 36, Catalina 38)
1) This is not an oil pressure sender. A sender is what drives an oil pressure gauge. None of Catalina's panels were equipped with a pressure gauge. They only had a low oil pressure warning light and buzzer. This is the proper oil pressure on-off switch that activates the low oil pressure warning light (and warning buzzer if your panel is so equipped) in the event of low oil pressure.
2) Regardless if you are installing an oil pressure sender or an oil pressure switch, never add any type of Teflon tape or pipe joint compound on the threads. The sender or switch are modulating the connection of the instrument to ground by way of the engine block. If you insulate the threads, they can't make the connection to ground and the instrument will not function properly.