I was out yesterday and my port side motor oil pressure started bouncing at higher RPM's. As soon as I pull the sticks back it jumps right back up. Lowest I saw was 18 psi and it would jump to norm 65-70. On idle is normal, I'm thinking it the sender... I kinda poked back there and looked for it but did not see it. When running in chop it seemed to bounce with the way the boat was bouncing. I checked the oil... Level was fine and look me on the stick(only 4 hours on the oil). It was nice and thick(no signs o aeration as far as I could see.

The sender is mounted on the engine block below the # 7 spark plug. Sounds like the wire may be loose.

Or your oil pickup may have come loose.

I'm hoping it's not the tube

test it with a mechanical oil pressure gauge taking the sender right out of the mix plus its connections.

Also make sure your oil level is correct and not over filled. Or making oil

Make sure you are using the correct motor oil viscosity and a quality oil filter. the simple things first and foremost.

I run royal purple and use a K&N filter. I have always ran that setup without issue. I'm prob going to take a look at the sender on Thursady... Se what that brings. Under #7 spark plug ...anomie know if it's the same on small blocks?

What gauge brand at the dash ? sometimes it is very wise to match sender up to gauge package brand. Its about matching ohms of the sender to the gauge. Just saying as a rule of thumb.

Bad sender....

Had the same thing happen on mine. Found some corrosion in the main plug of the engine harness. Cleaned it up, all good.

A cheby is a cheby, the holes are in the same spot, big or small block.........1,3,5,7 down the port side.....2,4,6,8 down the starboard