2005 175 hp Mercury optimax, how do I test oil pump?

[SparkieBoat]

I just purchased a 2005 175 hp optimax. the water filter going to the compressor was clogged and the over heat alarm wire was separate from the engine over heat alarm wire. I got a used compressor and the engine cranks and runs fine and fuel pressure is 10 more than my air pressure like it should be. everything is good, but I removed the top oil hose going to compressor to check for oil while the engine was running, and nothing was coming out of it. I am not sure what I should expect, how can I test the oil pump?

Thanks Sparkie