Check the manufacturers!
While many boats are referred to as "Hypalon" boats, they are not all alike. Hypalon is registered trademark of DuPont for the chemical chlorosolfonated polyethylene. Fabrics are coated with it to make them airtight. Usually, fabrics used for boat construction that are referred to as Hypalon are relatively complex multi-layer laminated fabrics.http://www.dupontelastomers.com/products/hypalon/hypalon.asp?redirect=hypalondotcomhttp://www.pennel.fr/Pages/orca_infla_boat_home.htmMy boat is made of Orca fabric, a product of PENNEL & FLIPO in France. Maintenance instructions from their web site:"MAINTENANCE In all cases, it is best to wash the material with soapy water, or with diluted bleach (hypochlorite) or ORCA® nautical finish Exceptionally, a cleaning with a solvent of Methyl Ethyl Keton can be tried, on boats used daily for example, but it is relatively sensitive because it must be homogeneous and must respect the regulations (toxicology, environmental protection) in force. Finishing products, such as silicons or others, are not suggested."My recommendation is to check with the boat maker, fabric maker before using anything stronger than detergent on these things, and that goes for waxes and coatings, too, especially silicone-based stuff.