To foam or not to foam
 

Yesterday I saw a episode on ship shape tv and it showed them installing a gas tank and they foamed it in and then glassed the top in between the tank and the stringer covering the foam. I have heard both side on yes to the foam and no to the foam and it's pro's and con's. So what is the consensus on the best way to go?

Shipshape TV is about the LAST resource I would consult on any serious boat work, especially installing a gas tank! Griviskis appears to only know what his sponsors tell him, and I'm not sure he even understands that. Foaming in a gas tank is about the worst way to install it! It allows water to be held in contact with aluminum, causing crevice corrosion. I think most boat builders do it because it's cheap and easy! Even Potter did it on his later models, but Carl Moesly never did. It cost him more because then he had to ventilate the bilge, but he knew that was the right way to do it! Although I've removed my tank a couple times to inspect it, I'm still running the original 1972 tank, which was not foamed in!

Dave Pasco wrote an excellent article on How to Install an Aluminum Fuel Tank that explains the process in great detail. About the only thing I'd add is that I'd paint the tank with an etching epoxy primer and maybe some coal tar epoxy first.

you're quite correct !

ventilation is the key

chemically etch priming ANY aluminum surface,before coating - that's required.

Thanks. Tank got the coal tar treatment. Now just need to source the plastic strips.

Yep, like Denny sayes.

I have a later Potter model (1977) and my tank was foamed in from the factory. Tank lasted 33 years but eventually corroded as Denny said above. I put a new tank in and did NOT use foam. I DID put runner strips under the tank on the fiberglass tank support

Potter tanks were not foamed in

Yes they were (Some in later years)...guaranteed! I'm the original owner of our 1977 23' Sceptre. The fuel tank was definitely foamed in from the factory.

I'm doing a 17 Mako right now, and those guys almost all foam their tanks in, but I'm going with the Pascoe method.

Ok. My 1974 tank was not foamed in. It was bolted to stringers via 4 brackets.

My 76 was foamed in from the factory. When I pulled it, the corrosion had just barely gotten through the aluminum in a couple of spots on the sides.