Audio gauge meter testing of a steel hulled houseboat. 4.4 mm is 0.1732283 inches. Many steel boat builders are using 1/8th inch (0.125) material.

Audio gauge meter testing of a steel hulled houseboat. 3.9 mm is 0.1535433 inches. Many steel boat builders are using 1/8th inch (0.125) material.

Thermal imaging shows this bottom is uniform in thickness. There isn't a lot of temperature difference showing.