Until the wet and rotting wood completely dissolves and is eaten by insects, there will not be a hollow sound. Tapping with a hammer doesnt mean anything
If it's wet, time to repair
I buy a tarp every few months to recover the Fiat. I have a canvas tarp covered by a vinyl / poly tarp. The vinyl / poly lasts a max of 5 months. They do not last in sunlight and wind
Covering a boat, I would go with canvas
what brand are you buying? Sierra or GLM?
Generally lack of cooling water flow is what causes the impeller to destroy itself, or the kits you are buying are old. Rubber has a calendar life that starts the day its molded, not when its used.
