New (used) muffler.. which way is up?

[deepsushi]

After a some long fishing trips where I spent the day trolling I realized that the v-8 growl out the straight exhaust on the inboard was too overwhelming. I started looking for a muffler and low and behold the right one popped up on Ebay and it is now mine!

The muffler has dual 3" inlets and a 4" outlet which is offset. My question is which way is the proper orientation to install it? I can see the baffles inside
the muffler and my guess is that the outlet needs to be mounted on top so that the gases pass through the trapped water. Anyone know if this is correct?