oil pump won't seal

2001 mercury 15 hp 4 stroke bigfoot Serial is 0T2897??

It broke an intake spring last summer and I just got it back together but it puked all of it's oil out in about 5 minutes.

I think it leaked from between the oil pump and head. Can anyone advise if this looks right?
The parts diagram shows a gasket on the oil pump and an O ring over top. Like this:

There is no groove on the pump to accept the o ring:

There is no groove on the head to accept the o ring it's not big enough to hold the o ring:

I have checked my parts diagram and my service manual. Both show this o ring in this location but when you install it this way and torque to specifications the gasket floats because the o ring creates to much space.

I am about to install it without the o ring.
Can anyone advise? This just can't be right.
BTW: the o ring came from a sealed factory package with the correct part number on it.

The O ring part number is MERCURY 25-825462

Update. I tried 4 or 5 times to seal it with the gasket and o ring specified by the parts diagram and service manual. When torqued to specs. you could fit a feeler gauge between the oil pump and gasket. It could not possibly seal. I even tried over tightening it until the bolts stretched. Still no seal.

I finally sealed it by installing it with the gasket and a thin bead of RTV silicone where the diagrams called for an o ring. I also used a set of three new bolts. I ran it this weekend and its sealed and runs like a top.

At the end of the day I don't know if the o ring (in a sealed mercury bag) was the wrong size or what but it's sealed now.