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using a meter, I came to the conclusion they are more of means of telling me there is more moisture here than there.
In this case, the readings seem low overall.
I would replace the through hull drains.
When you fet them out, a shop vac directed at the openings will tell you whether there is water or moisture.
Seal the new drains well and go fishing.

Yes, newer whalers will register more moisture around the transom and through hulls, than along hull sides.