Another H31 false bilge question

[Fashin]

Hey guys,

Just bought a 1985 hunter 31 and love the boat, but have been tracking down the ridiculous stench that comes from the bilge. Searched all over the net for a solution and found threads regarding the false bilge on hunter 34s, but still unsure if the 31s actually have a similar sized false bilge as the 34s. When I was checking out my bilge I found that the fiberglass was slightly cracked and if I would press on it black stinky water (smelled worse than a dead body) would seap out. I was able to get the aft side chiseled out, but there is almost no space in between the so called liner and the false bilge. Before I go and do something stupid like drill through the hull, is there more space if I was to drill down into the bilge?

 

[Benny17441]

It is not recommended that you open up the bilge liner as it would release fouled water smells; but seeing that you are past that point you need to look at what to do next. Let's define the problem; gallons of water from different sources get trapped in the hull stringers below the sole and the bacteria in it fouls the water and creates a foul odor (just as bad as a dead body). That water gets released piecemeal into the bilge usually by boat motion. The portion that gets into the bilge liner is usually the latest accumulation and is clearer than the more dense goo that will remain at the bottom. This top layer that makes it into the bilge liner acts as an odor trap, reason why I do not mind having always some standing water in the bilge. I have never done it, but I know some that have cut out a piece of the liner to be able to inject a cleaner and to be able to suck some of the fouled water out. The reality is that it is impossible to get to all the water and goo out and that it will add significantly to the maintenance burden to periodically have to treat and flush out some of the water. Allow me to suggest that repairing the current crack and sealing off the bilge liner might be an overall more practical solution. I do agree that you now need to provide some treatment to get at least the immediate area around the bilge under control. You can disconnect the bilge pump and fill the bilge to 3/4 capacity with fresh water and add a measured amount of cleaner and disinfectant and then go for a brisk sail to let all that slosh around before you return and connect the pump back up to discharge the flushing solution. There are some biodegradable products that will not harm the environment. I do this about once every two years but I suspect that if I broke into the liner I would have to do it a lot more often. Manufacturers have been building boats with what you call a false bilge for decades because it is the best way to address the problem and all kinds of people have tried and not come with a better solution. Good luck.

 

[Allan12210]

And now a different perspective. I have never regretted removing that bottom of the hull liner. It allows for complete drainage of trapped water in between the liner and the hull where it becomes a festering soup. I believe on your boat the distance to the actual hull is closer than on my 34, but there is still a distinct, separate layer of the liner and the hull. The liner is about 1/4" thick with a piece of plywood (now rotten) under it. The hull is 1-3/8" thick on top of the keel. Cutting carefully you should be able to start peeling pieces up. After mine was completely removed I remounted my bilge pump right to the bottom. With a dripless seal, my bilge is always dry and there is zero smell.

 

[SFS]

This thread may be of interest to you:

False bilge issue Hunter 34

Just started new winter project false bilge issue. Have owned this boat senses 1983 well Over 30 plus years with this false bilge issue. I have always kept the bilge clean, always flushing it with fresh water and cleaning products every weekend. I never could get rid of this foul odor that...

forums.sailboatowners.com

The thread is about H34s, but several people that posted modified their H31 by removing the liner in the "bilge". I corresponded with one of those folks (can't remember who) to get the specifics, and the approach was just like it would be on a 34, except for some slight differences in thickness of the liner. For an easier, less involved approach, see posts 28 and 55 in the thread

I had the same concerns as you, and never did remove mine. But I suspect it is worth the hassle, and you only have to do it once.

 

[Fashin]

I drilled the floor of the bilge and here is what I got can some one tune in?

 

[Allan12210]

The white layer is most likely the hull liner. Is it separate from the non-pigmented piece? Did the non pigmented piece break off or cleanly separate from what is below it? Did stinky water follow that piece up when you removed it?

My thought would be that the hull liner may not have the piece of plywood under it like many of the H34's do. The liner is still a separate step in the manufacturing process where it is bonded to the hull. It should be physically separate from the hull at the bottom of the sump area.

When I drilled mine out with a larger hole saw, I took the center drill out so I would not poke down too far. It looks like in your picture, that pigmented layer is all the farther you need to go to gain access to the trapped water that fills the hull up to the next set of limber holes opening up the liner for some water once it gets really full to cascade into the sump. Notice I don't refer to it as a bilge because that is at the inner surface of the hull (under the liner).

 

[Capt Robbie]

Fashin, good luck on your quest to remove the dead body stink from the false bildge. Allan is spot on with his comments about the false bildge, the problem with both h31 and h34 are almost identical, after the modification is done and flushed the boat odor is gone.
I did this modification a few years back and posted pics and how to, search my history " h34 false bildge" and what I used to clean it out I think you may find it helpful