"I have never read any stastis
"I have never read any stastistics on the water logging problem and floatation foam required by the CG for boats under 20'. The professional that replaced the transom on my boat stated that he sees it all the time on boats that were built using open celled foam. I would presume that since the foam is like a tight sponge that it will absorb any water it comes into contact with over a given period of time.
I first noticed it in my boat when I drilled some pilot holes in the floor to add different seating. The wood was solid but water logged. I used a hole saw to see what was under the deck and steam rollled off of the saw as it cut through the wood floor and exposed the floatation foam--looked just like a tan watermelon; nice and juicy.
Every pilot hole I drilled for anything was like drilling into a natural spring--even the transom when I added a transducer. You can purchase a moisture meter to measure the moisture content in the wood and flotation foam of your boat or just drill a few 1/8th" holes in inconspicuous areas of the hold and inside the transom and then seal them with polyurethane marine sealant. The floor has to come off to get the wet foam out and dry the stringers and transom if they are only wet and not rotted like mine were. Drains are drilled--USE A DEPTH GAUGE ON THE DRILL BIT SO YOU DON'T DRILL THRU THE HULL-- 1/4" TO 3/8" DEEP at the bases of the stringers, engine mounts and transom and vents are drilled at the top and sides of the mounts and stringers and above the waterline of the INSIDE of the transom until you find dry wood.
You can make a manifold drain out of PVC tubing and a 1" PVC pipe and then conect it to a shop vacuum and let it suck out the water. Then injecting lacquer thinner into the upper holes will force out the remaining moisture.
BIG FIRE AND SUFFOCATION HAZARD DOING THIS METHOD--BOAT MUST BE WELL VENTILATED AND YOU SHALL WEAR A RESPIRATOR WHEN ENTERING THE HULL OR ANY ENCLOSED AREA OR YOU WILL BE OVERCOME BY THE FUMES AND DIE.
A safe alternative is to suck out as much water you can with the manifold system and then install a dehumidifier in the bottom of the boat with a drain hose out of the drain hole. Now encapsulate the boat in 3-4 mil plastic sheeting in a tent manner. Installing a fan in one end of the boat keeps the air moving and hastens drying. Leave the boat outside in warm weather to allow the sun to bake the inside of the hull dry. The fan keeps water from condensing on the inside of the plastic sheeting. The sheeting will hold and seal better if you use the heavy clear tape that is used for installing temporary plastic storm windows.
When all is bone dry, Clear Penetrating Epoxy Sealer or CPES must be injected into the top holes--RESPIRATOR REQUIRED FOR THIS STEP--and allowed to run out of the bottom holes. The overflow of CPES can be captured and reinjected before it sets up. This process needs to be done 2-3 times to ensure enough of the CPES gets into the wood to seal it.
Then there is a several day open air drying period while the solvents in the CPES evaporate. It may take 5 days or 3 weeks for the CPES to dry depending upon the temp. When it is done drying, no odor will be present and the boat's structure will be strengthened by the epoxy enhanced wood. Plug the holes with a fine sawdust and epoxy puddy. It will never absorb another drop of water again.
When replacing the floor, cut the 5/8" exterior plywood to fit and then saturate it with 2-3 coats of CPES all over every piece. Install with 1-1/4" SS screws about every 6-8" and a liquid dish soap bottle with 1/2 to 3/4 cup of CPES. For each screw installed, first squirt a 1/4 teaspoon of the CPES on the floor and drive the screw thru it and the CPES will be drawn into the hole with the screw.
Next, to finish off the floor for strength, use epoxy to attach 20 oz. fiberglass sheeting to it per directions.
DO NOT USE CHEAP POLYESTHER LIKE BONDO. IT WILL NOT STICK TO EPOXY!!! EPOXY WILL STICK TO IT BUT NOT VICE VERSA!!! BEEN THERE AND DONE THAT!!! IT WILL PEEL LIKE A HEAD OF LETTUCE WHEN IT DRIES!!!
Layup and Leveling or L & L epoxy is easier to work with since it has a longer setup time--hours. Epoxy glues are like soft butter but setup in 10 to 30 minutes depending upon the air temp. Make small batches and place the container within an ice filled container and it lengthens the work time a little--stir constantly since once the chemical setup reaction starts it genrates heat and cannot be stopped. Unless you are experienced with fiberglass installation, work in small areas at a time. Use a stiff paint brush to dab the F'glass into crevices and corners. A floor glue trowel will spread both epoxy L&L and glue quickly.
Google "ROT DOCTOR" for more info. There are several brands of L&L and epoxy glues on the market--none are cheap--but all perform the same job when dry."
