Forty-two midshipmen were overcome by carbon monoxide last night in a dorm at the US Merchant Marine Academy in Kings Point, LI, police said.

The victims, all at Barry Hall, started reporting feeling ill just before 10 p.m.

Cops said 39 were treated at area hospitals. The three with the highest CO levels were helicoptered to Jacobi Hospital in The Bronx, which has a hyperbaric chamber. All 42 were conscious.