The reason I ask is my Johnson 50 hp hasn't been running good at wot the last couple times out... I checked it out today at the house & noticed that after I pumped up the bulb & the inline filter being full, it went down to about an 1/8 full pretty quickly after starting the motor.... Is this normal or do I have a fueling issue?

Poor running at wot, but idles good, can be an air leak. Possible your lines are sucking in air some where or a bad fuel pump.

Quick way to troubleshoot this is to manually pump the primer bulb at wot, if the wotor runs good then it is possible there is an air leak or bad fuel pump.

Your fuel filter should stay full.