changing oil pressure

[hedosurfer]

1993 mercruiser 5.7 bravo carb 8 cylinder. recently the oil pressure gauge has been just under 40psi from 1000 to 3000 rpms. if it does a slow idle it drops to about 20psi. over 3000 rpm it climbs to about 50psi. it will drop below 20psi if decrease speed quickly. on idle it stays around 20 but the alarm never goes off. it is the original engine with 618 hours and 18 years with original oil pump. could this be the pump beginning to fail like a fuel pump failing at low rpm but loading at higher rpm?

 

[chiefalen]

verify you oil pressure sender. By the way anything over 10 is good. All that might be needed is the sanding of the wire that connects the sender to the gauge on ether end of the wire.

Or the wire itself is going. Or the sender.