You've already had a couple of good suggestions
Especially the first one! :dance:
If the whole boat stinks, the culprit(s) are most likely permeated sanitation hoses and/or a bilge in need of a real cleaning that includes flushing all the dirty water out instead of just just dumping in some bilge cleaner and calling it done.
Odors are always strongest at their source...so if it's your hoses, the odor will be strongest in the lockers and compartments the hoses run through and the area where the tank is. The isn't likely to be source of any odor INside a boat, but if the tank discharge fitting is at the bottom of the tank, the pumpout hose will be the first to permeate.
If the shower and/or icebox drain into the bilge, it's a sure bet that the bilge is at least one source of the odor. Hunters are also notorious for a "grid" under the cabin sole that doesn't drain well, if at all...allowing water to sit and become a real primordial soup that can easily make a boat smell like a swamp or even a sewer.
So first thing to do: find the source(s) of your odor(s). Once you've done that, we'll know how to eliminate 'em for good.
As for my book, I suggest you check out the link in my signature to see how it can help you.