This is likely to be Formaldehyde. This is a common problem in motorhomes and mobile home/trailers. It is used to produce glues used in the manufacture of particleboard, plywood, veneers, and other wood products. It can irritate the eyes and mucous membranes, resulting in watery eyes. When the temperature rises it is most pronounced, such as a trailer that has been sitting in the sun, locked up, with no ventilation. Maybe try opening up the boat up and letting it breathe for a few days?