Double bottom bilge

[ahun]

So, we won't go anywhere far for awhile, and for this and other reasons we started a complete refit and renovation of our boat. It's the continuation of the mast replacement (see in another thread). We detected a possible diesel leak, ripped up the floor, removed and going to replace the s/s diesel tank, refurbish the water tank, clean the whole 'good old boat' etc.

What I found in the bilge was (besides the atrocious smell) that it had a plywood bottom fibreglassed to the hull quite hermetically, and underneath there is a cavity that is partly filled with polyurethane foam. The keel forward to it is concrete (at least on the top) and dropes down in two steps aftwards. The diesel tank was under the floor in the middle of the boat and the leak seem to have seeped down via the plywood, that separates the concrete sections of the keel and eventually to the cavity under the bilge. As the bottom of the bilge was so well done, plus it didn't rot, it stayed there. When I drilled a hole to it, this oily water started to come up and filled the bilge a few time before it stopped. The smell was clearly like rotten, anaerobic swamp smell.

Now my problem is two fold. One, is how to flesh out the remaining contamination from under/between the keel. Two, what to do with bilge. I would prefer to get rid of this ply wood bottom, but it will be impossible without removing the engine. So maybe just a section of it. Then I should fill the cavity out with something else than the foam and create a new bottom for the bilge.

Any advice and idea is welcome.

Thank you.

[ahun]

To get a better picture, I cut out the bottom of the bilge. I think the Po's just drained the engine oil into the bilge when they changed oil.