Someone went a little to far with the undercoating. Rhino Sealant
Rhino® GI Unloader Designed to Dispense High-Viscosity Adhesives and Sealant Materials, Suited to Medium-Thick Viscosity DIY RAPTOR LINER | MAKE YOUR BED / TUB BADASS Sealing my aluminum boat using flex seal and topping with truck bed liner spray. Will update on finish product once done, might Rhino-Grip Interior/Exterior Universal Primer Sealer is formulated to block most stains - water, smoke, ink, markers, and tannin. Rhino-Grip has exceptional ...