SV Pilgrim - 1979 Morgan 382 - Homeport: Beaufort, NC

Sunday, August 3, 2014

Bilge Modifications - Part 1

As I discussed in the Installing A Holding Tank In The Head post,  the original Morgan 382 design placed the holding tank below the bilge in the aft lower section of the keel.  Below is a blueprint of the area from the original plans –
Blueprint of the aft lower keel on a Morgan 382.
Pilgrim developed a leak between the floor of the bilge and the holding tank area.  I learned from the Morgan 38 Message Board, that other M382 owners have dealt with similar issues.   

My best guess is that the bilge floor leaks around the plumbing fittings.
Floor of bilge is perforated by plumbing for the holding tank. From aft (left) to fore (right) - PVC pipes serve as inlet and outlet for waste, grey tubing is holding tank vent, and plug with wires is sensor that indicates tank is over 3/4 full.
The new holding tank installed in the head eliminates the need for an inaccessible void in the lower keel.  I prefer to have access to the area to permit visual inspections and allow Pilgrim’s bilge pumps to properly eliminate all standing water inside the vessel.

I began by drilling 3/8” holes to serve as an outline the area to be removed.
Drilling 3/8" holes to mark the perimeter of the section to be removed.
While drilling the holes, I realized that creating a series of drilled holes would generate less fiberglass dust than other either using a jigsaw or a grinder with a cut off wheel. 
Series of holes complete.
The excavation did ultimately require a combination of drilling, jigsaw, and finally grinder with cut off wheel…

Working with power tools in the confined space with limited access required patience.
Eventually the fiberglass bilge floor succumb to my efforts.  I will spare you the image of fiberglass dust floating atop the black water below and the details of using a shop vac & scouring pads to clean the area.  If you want all the images check out our Bilge Modifications Photo Album.
I was not expecting the floor to be a consistent 1/2" thick.
 The consistent 1/2”+ thickness of the bilge floor surprised me.  The thickness of the material leads me to believe that it serves as a structural member of the aft section of the keel.   Good thing I only removed a small section from the center of the floor.

The source of the leak never revealed itself.  I’m still betting the leak existed around the PVC pipes that served as the inlet and outlet for the waste.
I believe the PVC pipes were the source of the leak(s)
Pilgrim now has an upper and lower bilge area.

The upper and lower bilges are now clean and dry.
Our plan is to allow a few weeks for the lower section to completely dry out.  We will then apply barrier coat, paint, and finally install bilge pumps & float switches.


  1. An ingenious (but difficult to maintain) solution by Morgan! Given the thickness of the layup, I'd agree with your assessment that the leakage would be at the PVC pipe/fiberglass joint. I believe that it would be difficult to get a chemical bond between polyester resin and PVC, and the extruded pipe is much too smooth for a sound mechanical bond. The best solution would probably be something that involves a deformable gasket.

  2. Oh, and those cracks in the resin layer at the bottom of the "tank"? There may be seepage from the previous tank contents coming out of them for some time to come. You may want to leave a 1/8" deep layer of bleach in there for a while...

  3. Robert, Thanks for the suggestion. I'll keep and eye on the cracks in the bottom layer. Thus far I am surprised by the lack of odor and seepage from the former holding tank. I suspect that it did not get much use from the previous owners.