HELP! Oil Pressure DROPPED 0 on elec gauge 20 on mech !!

[castone001]

OK im baffled and will be taking the motor back to the builder.....
I have my brand new 460 .30 over mild cam, high rise tunnel ram with 750 Demon in my boat, you all seen the pics :)
Put 5 hours on it at Elsinore with never a blip and solid oil pressure at startup of 75 pounds, brand new Autometer gauge and seding unit as well. I did notice the pressure doen to 60 after running it a bit but never lower than that.
So all confident I was and off tot he River for 5 days over the 4th. First two days not a problem. Kept it under 4000 at all times, cruised mostly at 2800 - 3500 and occasionally quick jump up to 4000 for short period then back down to 2800 area.
Welp coming up from Topaq on the third day I now have 8.5 hours on the motor. I notice the needle going to 0!!!! I immediately shut down. Got towed back to ramp. Checked the oil and it was maybe one quart low. Put it in and fired real quick still no pressure. Got my buddies new sending unit in it and was able to get 15lbs to read on the gauge.
No lifter rattle or rod knock thank god!
Took it back home and finally had time to sticka mech Oil pressure gauge on. Fired it up and only got 20lbs of pressure.
Oil is full, there is no oil in the bilge??
Any clues?

[Rexone]

What kind of oil filter? Several people have posted regarding problems of this type with Fram Filters.
Other possibilites are broken oil pickup, clogged oil pickup (silicone or other material).

[quiet riot]

Make sure to check the clearance between the pan and oil pump pickup, if too close it can suck the bottom of the pan to the pickup and close off the oil flow as you increase rpm. Common with slight variations in pickups on aftermarket pumps just after a rebuild.
jd

[LakesOnly]

Start with oil filter since it's the most readily accessible. Put a quality filter on. And don't toss that changed-out filter just yet. Cut it open first, it may very well have a story of its own to tell.
LO

[FASTJTBT]

Installed A Dooly Pan And My Pressure Would Idle At 10lbs Then Go To Around 40lbs Wot This Was On A 468 The Motor Is Still Going Strong After 10 Years.