Almost a V-20

You guys seem to have your Ray Hunt designs down pat! Thats an extremely rare boat, I've never heard of them......its a 1976! That thing is old as the hills! Soggy stringers, soggy transom, rotted out gas tank. A gas tank, that unlike Wellcraft who are still in business, you cannot get a replacement easily. Maybe custom fab = Beaucoup $$. I'm not sure I'd even trouble myself with a look.

Anybody know of any sure fire, easy to do methods for inspecting all of the items above? W/O drilling a ton of holes how do you check for rotted floor & transom?