Sounds like permeated hoses
The odor is not coming from inside the tank, nor has your tank permeated, but I'd bet that your pumpout hose has.Yes, I know you replaced the hoses last winter (did you replace ALL of 'em?), but if you tried to save money by going with cheaper hose, it CAN permeate very quickly. Happened on my own boat...new #148 white hose permeated in less than 90 days. Unfortunately, new hose is the only cure.I dunno how many times I've posted--AND it's in my book--that the holding tank, unless it's leaking, is never the source of odor INSIDE the boat...'cuz odor from inside the tank has only one place to go: out the tank vent line. So nothing you do to the tank or tank venting will cure odor INSIDE the boat! The sources of odor INSIDE the boat are sanitation hoses, wet dirty bilges and/or sumps, trapped water below the sole...or any sea life that may have gotten caught and has died and decayed in the channel in the rim of the toilet bowl (but that odor would be confined to the head, it would not permeate the whole boat).So do the hot wet rag test on your sanitation hoses...I'd bet money they're your culprit...at least the pumpout hose, anyway. If I'm wrong, check any y-valves and/or macerator pump for leaks.There is a "band aid" that'll get you through the summer: wrap the hoses in Saran Wrap (only the Saran brand will work, so don't use Glad or anything else). Wrap 'em tightly and seal the ends with electrical tape.