I purchased a brand new long block 502. Only second run out on it and it's showing I have Low oil pressure , checked the gage and the oil is fine, any suggestions?

Change out the oil filter and have it cut open to see if the main bearings are in there, also test with a mechanical Guage

you sure you put the oil lines on right.outside line goes to the outside of the oil filter pad.

What kind of new long block? If it is of the automotive type, the bypass in the filter pad is probably an 11 lb unit and is not setup for a filtering system with a cooler. You will need to swap that over to a 30 lb bypass before you roast the bearings in the motor.

All good answers. How low is the pressure and at what rpm? Brand new automotive long block or marine long block? The marine block will have the 30lb oil bypass valve in the block under the oil adapter and an automotive has only 11lb. If it has the 11lb bypass, the oil will at some point not get filtered or cooled.

MATT, we must have been typing at the same time. Great minds think a like!

Define " low " also,,, at idle or ,,, running ????

Nevermind,,,, 3 people said the same thing at the same time

It's a mercruiser 502 long block. It was at 40 the first trip out, then the other day it was bouncing back at forth from 10-20from idle and running