Here is a post about boat and head odor that I put up on the downeasteryachts.com website forums in a conversation of how to get rid of lingering odors on boats.
We got into this on valkyr this past week… it was so much worse than just old plumbing. We found a leak in the system that raw sewage had been leaking out of for many many moons.. It was a hazmat style operation to scoop the shit out of the little compartment under the aft end of the vberth where that built in seat is. We found that a decent painting respirator from lowes works wonders for getting up close and personal with shit. After scooping it out and then cleaning the respirator does wonders when you paint the bilge areas After cleaning out the leakage we came back the next day and cut out and removed the head, all hoses, fittings and the holding tank. We then did a single rough clean and rinse of the compartment the leakage was in and the big v-berth compartment that the holding tank had been in.
As to odor.. the next day we cleaned all the lockers and bilge areas twice with oxyclean and a brush on a handle, then we cleaned twice with the brush and a very strong clorox solution. the second clorox cleaning we put it on strong and didn’t rinse it till the next day. Just left it brushed on. The next day we cleaned twice with vinegar water. We used the vinegar at roughly 50/50 with water.The first time we used the brush to slop it on heavy. After everything had been covered we went back with one of those foam sanding blocks and the bucket of vinegar and lightly sanded from the chain locker down through the bilges under the v-berth as well as all the closets and cabinets fiberglass surfaces (the sanding was a two for one idea. It was the last vinegar treatment as well as wet sanding the fiberglass and existing bilge paint in prep for us painting all the surfaces in the bilge). We also took the brush on a handle and scrubbed all the wood and every surface in the v-berth with 50/50 vinegar and water. We soaked it down good and scrubbed then took a hose down below and rinsed everything of with it. the sides of the cabin where the teak strips make the walls, the doors, door frames etc.. we must have pumped a hundred gallons of water through there rinsing. Gave the bilge pump a good workout. After rinsing we took paper towels and got as much excess water off of the wood as we could and then left it to dry overnight.
The next day when we got back we really worked hard to find some odor and couldn’t. The v-berth now smelled clean. Actually the rest of the boat (saloon/galley area) still has a faint old boat smell. So the v-berth is now odor free. In my opinion the vinegar treatment was the most effective in removing the ingrained odors. I think that I would use the same methodology in the future. A good soap and water scrub to get the grime and dirt cleaned up. Then a clorox disinfecting followed by a vinegar scrub and rinse. The vinegar removes all traces of the prior treatments also and when it drys leaves no odor at all behind not even of the vinegar.
We decided to go the extra mile and spent two days painting the bilge areas, and inside all the cabinets and closets with brightsides gloss white one part polyurethane paint. We put two coats on and it looks awesome. Zsanic did the majority of the painting as she could get into some of the tight areas a lot easier than I could. We found that a can of acetone and a roll of paper towels were a necessity. Somehow you were constantly getting a drip or smudge of the paint somewhere on the wood above the bilges as you moved around and braced yourself. The acetone on a rag pulled the paint right back off. As you can imaging the odor of the solvents in the paint were overwhelming. We were not allowed to work in the v-berth area unless we were wearing the respirator, we also got a cheap box fan and it fit perfectly in the forward hatch pulling air up and out of the boat. Once the box fan was running you could stand in the v-berth door and not even smell the paint while we were painting. For the person in there painting it reduced the fumes by about 90%. With the respirator on you couldn’t smell any fumes at all. Even though brightsides is a one part paint and not one of the eviler two part polyurethanes it is still toxic and proper safety with respirators and ventilation is a must.
We are now reassured that by the time we have gone through the whole boat as we work our way back through the saloon and galley the boat will smell very sweet as opposed to the current slightly mildewy old boat odor. If we can knock out the odor from leaked sewage that sat in that forward compartment for months then the normal old boat odors should tremble in their shoes.