I just hand the heads , valve's, new rocker arms, and valve springs
done in the one engine

I took the boat out last night and after running under load for about
15 minutes the engine in question started to lose oil pressure.


Assuming that the headgaskets were changed and that you are not running
a drysump or scavanger oil system, there might be the possibility that
the oil drain backs from the cylinder heads are restricted.

This would cause engine oil to remain in the rocker area and not drain
back to the pan, causing the pan oil level to drop and, after a while,
resulting in the oil pump pickup drawing air and lowering your oil
pressure. Since you were probably on plane and moving around, lowering
the level a only a couple of quarts could result in this situation.

Since you did not say any lower end engine work was performed, one can
assume that the oil pump and bearings have not been touched so that is
not the issue. Also, it is not a ring issue since you said the oil
level is full when you returned to the dock.

You should be able to check the drain backs by removing the rocker
covers and visually inspecting the passages. They will be in the lower
corners of the cylinder head (I can not remember if the 454 has only
one in the rear or one in the front and rear).

Another possibility, although not really probable, is that the head
gasket or cylinder head has a slight opening to the crankcase from an
oil pressure passage and the oil pressure is leaking there - but I
doubt it.

well I got back to my slip and took a look at the oil filer , it
seemed to have some stuff in it as I assumed that it would, so I
changed it, and re started the motor.

As the filter filled the oil pressure gauge jumped up, but not as high
as it should.

Unless you have a non-bypass oil filter (I have not seen one in years
and years) then even if the oil filter was completely plugged, you
would still not loose oil pressure. This is probably not your problem

What kind of oil pressure were you seeing?

Thanks and good luck!

GPG