I'm running with the automotive version of the ZZ502 in my boat. The engine is fresh water cooled with aluminum heads. I did a parts swap from my older Mercruiser 454 but with the proper flywheel used on a 502. My oil pressure gauge reads 80lbs on start up. The block has a bypass valve as does the remote filter adaptor. Should I remove the bypass valve from the block? With a high pressure pump, what psi valve should I use?
Thanks in advance!

Some people remove the valve in the block (filter pad) and put a plug in there, others run the valve. If you do run the valve be sure to put a 30psi one in there. Typical automotive applications use an 11psi valve and you will lose an engine real quick with that!

Bypass valves (actually called filter bypass valves) work off of pressure differential. Not the psi you see on the gauge.

and don't forget to take the valve out from under the oil filter nipple.

I run the 30 lbs valve in the filter pad and removed it from the under the filter head nipple. I didn't use a plug because I didn't like how the ones I had fit so just went with the correct valves.

If I have it right, I've heard tell that the valve above the filter nipple is associated with using an automotive type oil cooler. That it is actually a good thing because it prevents oil drain back from the oil galley. It's all very confusing! I will go with a 30lb valve in the Mercruiser adapter as it was the original setup. I have been around engines for many years, but only recently learned of the valve used in the filter pad. Who knew?

Arcticfriends wrote ‘the bible’ on oiling issues with the 454/502 systems. It is referred to all iver the net.

click: oil pressure problems from stock hardware

I actually meant the valve above the filter threads, not the pad. Duh!