Oil Leak in 95 225

I have a 95 225HP yamaha I bought in february. I noticed earlier this winter that oil appeared to be leaking out of the oil pump area, I cleaned it up and it did not leak again. This past weekend the weather was the warmest of the season and I noticed it was leaking again. It appears to be leaking from the seal between the top of the pump body and the manifold that the oil lines run into. It also appears to be leaking from an outward facing flat head screw that looks like some sort of adjustment on the upper right side of the pump facing outboard. I backed the screw off slightly and it oozed oil. My question is (forgive my ignorance!) what is that screw for, if I tighten it all the way up will it affect the motor, and what is the rough cost of replacing the entire oil pump? I dont want to leak oil into the water and am worried about a pump failure which could damage the motor.
Thanks in advance for any advice you can provide!

[boats.net]

That screw is the bleed screw to bleed air out of oil pump, it may need gasket under screw replaced.