Originally Posted by nk235
... I am curious and tempted to try drilling a small hole into that platform that the muffler is screwed onto just to see what happens - if it is solid or hollow and if water comes out. What do you think? Dumb idea?
Not sure. You might try it -- but like erps says have a plan.
Maybe take a stroll around the boatyard looking for a similar aperture arrangement, so you can study how the tube seals at the aperture opening. This might give you some better insight into what you're potentially dealing with.