I am testing some glues now before I read the last posts. I glued some 2" x 3" pieces together. One pair with Titebond II and another pair with some spray contact adhesive I had around...It's 3M 77. It doesn't say it's meant for foam, but it didn't melt the foam either. I'll give these until tomorrow morning to set up and them immerse them in water for several hours to see if they come apart or not. It the glue holds up, I'll decide which to use. I know epoxy would work, so it wasn't in the test. Bassed on the comment above, I suppose the 3M spray contact cement would be better.

This is an all foam boat made by laminating the 1/2" sheets together, except for a piece of plywood that will be laminated in between layers 4 and 5 (from the bottom up) to secure the engine mount. The plywood is cut in a U shape with two narrow pieces extending forward to the front of the electronics compartment just to provide strength and rigidity. The hull thickness is 3" except for the 5" x 9" or 10" at the rear, where it will be only 2" thick as shown below. The overall dimensions are now 22"l by 12"w. I'm also considering painting it with latex enamel paint for more protection and to give the hull some gloss to reduce water drag.