I'm temporarily using a tarp as I must get it
dry inside.

I faced a similar problem last fall with my new project boat. I ended up
having a new cover made for it, which ran about $650. In hindsight it was
well worth the cost, as it's done an excellent job keeping the interior
protected from the elements (rain and snow).

Just a thought - my interior was completely water-logged when I purchased
the boat. I placed a dehumidifier in the boat, with the drain hose emptying
through the hull plug. I put the cover on and left it alone for a week.
With the thing baking in the sun, it drained a steady flow of water for
several days. After a week it was down to an occasional drip, and when I
took off the cover I was amazed. Everything was almost completely dried
through, allowing for a much closer inspection of the "questionable" wood.

Doug