2100V List to Starboard

[OldeBoy]

2000 2100V that we have owned since 2010.
I have noticed a 1" to 1.5" list to starboard with boat unloaded the past several years. (list may be slowly increasing) I have pics of it floating level in 2010 and 2012.
No new equipment has been added.
I am wondering if it has retained water underneath the floor on the starboard side.
If I remove the house battery from the rear transom compartment and reach thru oval hole in floor of battery compartment I cannot find a drain/passage from the locker floor to this rear bilge compartment under the battery. I did find a large oval hole between rudder area and area under starboard battery compartment.
I also noted evidence of a black watery liquid dripping from rub rail on starboard side on on last long road trip. (stained hull and trailer) Did not have this on port side.

Does anyone know if/where there are drainage passages from these starboard under floor areas?
Does anyone know what is under the floor, is there floatation foam under there that could have become saturated.
Thank you for your input.

[SONIC]

I don't think there is a drain hole as water isn't supposed to get down there, and yes there is flotation foam on both sides.

[KoolAid]

When on the trailer, dry bilge, put the plug back in. After a day or two is their water in the bilge?

[OldeBoy]

Usually have v drive area plug out when on trailer so haven't noticed accumulation.
Boat covered on lift with plug in during season. Usually drain a little out (1cm) or less when on lift after use. (To take care of inadvertent cover leaks(rain), driveshaft seal drips, skier drippage etc)
Off season boat stored inside on trailer plug out.

[KoolAid]

The foam couldn't become saturated because it is closed cell foam. Maybe water is in the two cavities where the plugs are for the engine mounts (where they through bolt into the stringer). There are two stringers on each side. One long one that goes about 2' from the nose and a shorter one which is about 8' long. There is a cap that covers the end of the stringers. Should be 3/4" plywood. Maybe there is an empty area there that the foam did not spread to. You may have to punch some small holes to figure it out.