Boat Suppliers Urethane Pour Foam

Expanding urethane pour foam is a two-part, closed-cell liquid foam system that expands rapidly when mixed. It's used for flotation, insulation, soundproofing, and filling voids in boat hulls, decks, and other marine structures.

No. This is pour-in-place foam, not spray foam. You mix the two parts, pour the liquid into the cavity, and it expands to fill and harden. Spray foam uses different chemistry and equipment. For flotation, coring, and filling voids, pour foam is the right product: just pour in lifts and let each rise before adding more.

Foam expansion is temperature-sensitive. For best results, both the foam and the working environment should be around 80°F. At 50°F, expansion can be reduced by 50% or more. Warm the product before use if needed.

Use 2 lb foam for standard flotation applications. It offers about 60 lbs of buoyancy per cubic foot. For added strength or to support a deck, 4 lb foam is a better option.

Once Parts A and B are mixed, you’ll have roughly 45 seconds before expansion begins. Stir vigorously for about 25 seconds, then pour immediately. The foam expands fully in about 5 minutes and hardens in 15 minutes.

Yes. You can pour in multiple layers, waiting 15 to 20 minutes between pours. This method helps control expansion and ensures complete curing without overheating.

Work out the cavity volume in cubic feet (length x width x depth in inches, divided by 1,728), then divide by the kit's yield for your density. At 80°F the 2 quart kit fills about 2 cubic feet of 2 lb foam, 1 of 4 lb, 1/2 of 8 lb or 1/4 of 16 lb, and the 2 gallon kit fills four times that. For a single closed pour, mix no more than about 10% over the cavity volume, and expect less rise in cool weather.

Yes. Once cured, urethane foam is resistant to gasoline, acetone, and most solvents. It cannot be dissolved, only mechanically removed by sanding or scraping.

Yes, you can pour foam into molds. For easy release, use a mold release wax like Partall #2 or line the mold with smooth plastic sheeting. Porous molds should be sealed before applying wax.

Yes, with care. Calculate the internal volume, and make sure the cavity is dry and sealed. The foam only flows a few feet before it expands, so for long, narrow spaces, over 5 feet long or under 2 inches across, results vary and you should test first. See our full guide on filling pontoons with foam.

Measure equal parts A and B by volume, mix hard for about 20 to 30 seconds, then pour into a dry, contained cavity and let it rise. It foams in seconds and cures rigid and closed-cell, so it resists water and adds flotation. Work between about 75°F and 80°F for a full rise, fill deep cavities in layers, and pour only as much as you can mix in one batch.

Density is the cured weight per cubic foot: higher density is stronger but expands less per kit. 2 lb is for flotation in pontoons, under-deck and bilge voids. 4 lb carries load under decks and around tanks. 8 lb and 16 lb cure dense enough to carve and shape for backing blocks and high-strength fills.

In a free rise at 80°F, 2 lb foam expands about 30 times its liquid volume, 4 lb about 15 to 18 times, 8 lb about 8 times and 16 lb about 4 times. By kit, the 2 quart kit fills about 2 cubic feet of 2 lb foam, 1 of 4 lb, 1/2 of 8 lb or 1/4 of 16 lb, and the 2 gallon kit fills four times that. Cold cuts the rise, to about half at 40 to 50°F.