No oil pressure at wot

I have a 95 sea ray with a 5.7 alpha 1 i/o with 319 hrs & 19 pitch ss vengeance prop. I usually run it around 3000 to 3600 rpm's, oil pressure at 25 to 30 psi warm, and temp around 170 with raw water cooling. When I take off I will go wot for a few seconds and then back out after it plans off with no oil pressure. From cold start I have 40 psi. ***-UMED oil gauge as others were unreliable due to the fact I don't get the buzzer. I have run it all season with no issues until today. After running it at 4200 rpm's for a few minutes and no oil pressure I backed out of it and heard the lifters raising cain. We let it idle for a while then ran it at 3200 for a few minutes with 25 psi. Stopped again and heard no noise from the lifters.This had happened the 2nd time I had run it. Figured out the marina that serviced it over filled by 2 quarts and thought maybe the crank was slapping the oil and foaming it. Changed it again and used a Napa gold full size filter and Amsoil 15/40 full synthetic. The marina used 20/40 synthetic. At this point thoughts are motor is worn out and oil is getting by the bearings and not holding pressure under heavy load or the bypass in the pump is not holding. The boat runs very well all day every day as long as you don't want to go to its top speed and I do from time to time. I have 6 350 small blocks in my work trucks from 1988 to 1998 with a lot less babying than I am doing to this one. LOL. Any help is appreciated.

Re: No oil pressure at wot

I had that same problem once, not saying its absolutely your problem but easy thing to check. Remove 1 quart of oil and try it again. My 5.7 would froth the oil with 5 quarts and while getting on plane and running in high rpm's same problem as yours. removed a quart, problem solved.

Re: No oil pressure at wot

I think that we have tried that except for going 1 quart lower. As I said in my post it runs great at or below 3600 rpm's but oil pressure is low a continues down the entire time we we go faster. Thanks for your input.