My anchor locker used to do exactly the same on my 6.5 Ocean.
The boat did not have a full cover, which left the anchor locker hatch cover exposed to the rain when on its trailer, and it was surprising how much water would collect in the locker during a short period of rain.
I tried to seal it several times and gave up in the end as I believed the water was pooling in the catch indents and running down past the seals into the locker.
Since I put a full cover over the boat I even leave the hatch cover off to air the warp and locker, and don't get a drop of rain water in there.
I really can't reccomend a full cover enough, as between use the boat gets fully dry.
RIBBED For extra pleasure.
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