I took an earlier suggestion and took out my sender, put in a nipple and ran the engine to try and pump out an dirt or obstruction. I took out about two quarts of relatively dirty oil. I had only run the engine for about 8-10 hours since the previous change so I was surprised to see the oil look so dirty. I ran the engine, all oil used was 10W-30 Valvoline, and had the same problem. Lots of pressure, 40+ lbs, during warm up and idle and during full throttle use good pressure, 50 lbs. On the way back in after about 10 minutes of full throttle use the pressure started to drop and went as low as about 18 lbs, engine temp was 160, from there the oil presure went to zero(from 18 lbs) in less than a second like someone had turned off the oil pump. I turned the boat off and let it sit for about 5 minutes. On restart I had about 20 pounds of pressure. It dropped again from about 18 pounds to zero(once again instantaneously) on the way back in. After about 5 minutes I restarted and had 20 lbs again. After I got back to the dock I started the boat intermittenly over the course of several hours. The longer I waited the more pressure I had. After sitting overnight I went out and restarted the boat I once again had 40 lbs. It seems like the oil filter is not the culprit as it seems after sitting for a while the problem resolves itself. I did not change the oil filter this weekend and had all of the same simptoms.

I talked to my engine builder and he thinks I have a sticky oil pump relief valve. Would and open valve cause me to lose all pressure in an instant? Even if it did how and why is the oil getting so dirty so fast?

I am begining to belive that I am going to havee to drop my oil pan, which will require me to remove the engine.