Ok well I found an interesting looking spring and screw in the bilge area. The spring is about 1/2" wide and 2 1/2" long. The screw is 1" long.
I found some other stainless nuts and screws that were dropped in there by accident as well. I am going out to make sure nothing else has found its way in to the bilge.

What else could cause this high water pressure. The port engine also gets hotter than the starboard at times (160-170 vs 140) after WOT runs. Oil pressure sometimes runs a little higher on the port engine as well.