I just installed my new 460 in my boat. The oil pressure is great at idle, and through 4600 RPM's it stays between 70 and 75 psi. I'm using a new high vol. oil pump and a new shaft.
The pressure drops to around 20 PSI like clockwork at 46-4700 RPM's.

I have a 10 quart Milodon pan on it. We set the gap on the pickup at a tick over 3/8 inch from the bottom accounting for the gasket.

This thing is FAST and sounds great. What the heck could be causing the drop? I'm using a K&N oil filter.

New bearings through out the engine, cam, mains and rods. All internals are new.

All clearances checked before the build.

Do you think trying synthetic oil say 5w 30 would help the pump? It would be easier than pumping 10W 40 regular oil and easier to get the oil through the motor.