[MC1600]

I’m really struggling to track down what’s going on here in the forward bilge of my ‘99 4000. The end of last season, I cleaned out what could best be described as mud. After being back in the water a couple months now, it’s starting to reappear. 

I can’t feel any wetness from above. Doesn’t seem to be coming from the shower sump. The only other thing that drains down this way is the evap for the forward ac. 

Anyone have any thoughts? Never seen anything like this before.

[Sans Peur]

Is you shower sump working? It could be spillage from that and as the water evaporates it leaves the soap and stuff.

[MC1600]

It is currently, but I did have a couple issues last season. Maybe this stuff had fallen aft, washed forward, and dried since I last cleaned it up. Will keep an eye on that. Thanks.

[Jfhaas]

My 97 had a similar problem. I hate to mention this but my holding tank was leaking.  After a great deal of investigating and cleaning it was determined to be holding tank. Purchased boat in 6/21..  The problem was the vent for the holding tank was plugged.  Pumping out the tank collapsed the tank slightly which put a crease in the aluminum. During winter had a new tank installed under the aft bed.  Able to get a 41 gal. tank to fit.  Pulling the old tank would destroy the aft stateroom..  Old tank was sealed and with a good deal of $$$ the problem is solved.  Hope your problem is simpler. Jack

[MC1600]

Thanks Jack. Fortunately, this stuff had no discernible odor, so I doubt it was the holding tank. But will definitely keep an eye on it. I got the area good and cleaned-up, including the shower sump, and it hasn’t returned yet, so fingers crossed.

[egstasea]

My 97 had a similar problem. I hate to mention this but my holding tank was leaking.  After a great deal of investigating and cleaning it was determined to be holding tank. Purchased boat in 6/21..  The problem was the vent for the holding tank was plugged.  Pumping out the tank collapsed the tank slightly which put a crease in the aluminum. During winter had a new tank installed under the aft bed.  Able to get a 41 gal. tank to fit.  Pulling the old tank would destroy the aft stateroom..  Old tank was sealed and with a good deal of $$$ the problem is solved.  Hope your problem is simpler. Jack

As a side note to the collapsed tank issue, I installed a TEE in the hose before the vent filter, and lead a hose from the TEE to the engine room ladder ending in a quarter turn valve.  Every time I pump out, I open that quarter turn valve so there is an other way for air to get into the holding tank.  The idea is to prevent the collapsed tank Jfhass describes.