Applications include these engines (and the boats that we are aware used these engines... There could be other combinations as well):
• M-12 (Catalina 25, Capri 26)
• M-2-12 (Catalina 25)
• M-18 (Catalina 27, Catalina 30)
• M-25 (Catalina 30)
• M-25XP (Catalina 28, Catalina 30, Catalina 34, Catalina 36)
• M-320 (Catalina 27, Catalina 28, Catalina 30)
• M-35 (Catalina 34, Catalina 350, Catalina 36, Catalina 38)
• 5424 (Catalina 38)
• M-50 (Catalina 42)

If you happen to drop the filter while removing the old one and are wondering how to install the new one, insert the small end of the filter (with the smaller i.d. but more red plastic) first. The end with the larger i.d but less red plastic should be at the bottom, just above the bottom cap.