Merc trim system cleaning

[glastronjohn]

I have 1990 merc 350mag, Alpha gen 1. The trim oil has been milky for the past few years so I'm cleaning and rebuilding the system. The trim pump has a plastic resivore with the a single bolt through the bottom. It's on the bench. I cleaned out the resivore and now want to get the bad oil out of the pump. Can I cycle new oil through the pump with it on the bench, or will I break something with the hoses off, or is there a better way? I want to get all of the old oil out before I put it back together.

I'll tackle the cylinders next. I have spanner wrench for the caps, 2 new seal kits and the merc instructions. I plan to clean the hoses and manifold out with solvent and an air hose. Any other suggestions?