Abstract: An acoustical enclosure for a marine engine generator set includes a squirrel cage fan powered mechanically by the engine and mounted over a large opening in an end of the enclosure. Air inlets are provided to admit external air into the enclosure. A large air flow results, allowing the generator to be operated at full capacity, even at elevated ambient temperatures. Noise is prevented from escaping out of the opening in the end of the enclosure by having the fan placed directly over the opening, where the solid plate of the squirrel cage fan reflects a portion of the noise back into the enclosure where it is absorbed by sound absorbing material lining the inside of the enclosure. A fan duct surrounds the fan and a cover is placed over the duct. The cover is also lined with sound absorbing material to further attenuate any noise not reflected back by the fan.