Hello, I need Your advice. I have purchased 1983 S2 9.2C sailboat . It is powered by 2GM20 Yanmar engine. It had oil light and the buzzer and they are working OK. Well, I am a car mechanic by trade, so I like to have as much of information about the engine vital signs. I have install a electronic oil pressure gauge and sending unit. When I start the engine cold the pressure is 40-50 psi. As the engine warms up it goes down. After about of 30 minutes of engine operation and at 2300 RPM cruising it goes down to 3-5 psi. Oil light and buzzer are off and engine sounds good. What should I think of this? Is this normal? I am running a straight 40W Delo oil. I like to get your opinion and advice. Thank You