I've had this musty, slightly diesel/oily smell coming from the bilge on my boat since I bought it. It would seem worse some days than others and a bilge sock got rid of the worst of it. It wasn't an oh my God smell, more of a I know it's there so it bothers me smell. The source was the mechanic who changed my fuel filters when I bought the boat last July and managed to spill quite a bit of fuel into the bilge and didn't do a great job cleaning up.
With the boat closed up for weeks at a time during the winter I really started to notice the smell.
So last week I sucked out the bilge with a shop vac, soaked it down and scrubbed it with Simple Green as a degreaser, rinsed it, sucked it dry again. Hit it with Spray Nine, scrubbed, rinsed and dried it again.
This weekend I'll clean/degrease the engine so I can spot if there are any leaks.
My Catalina 30 has two bilges. One under the cabin sole, and an upper bilge under the engine/transmission/fuel tank. Water entering the boat from the shaft seal drips into this upper bilge. Once this bilge fills to a certain level a bilge pump pumps into the lower bilge where a second bilge pump pumps the water out of the boat. This seems like an odd system to me. In fact on my buddies '05 Catalina 30 there is a pipe cast into the stringer that allows this upper bilge to drain directly into the lower bilge.
Is there any logical reason why I wouldn't want to just put a t-fitting into the line so the upper bilge pump could also pump directly overboard?
I realize there would be some back flow into the lower bilge but there shouldn't be much if the t-fitting is above the upper bilge pump.
Drilling through the structure of the boat in this area and adding a drain pipe is not an option.