Holley 0-80537 Model 4150 Performance Marine 750 CFM Square Bore 4-Barrel Mechanical Secondary Manual Choke New Carburetor J-style vent tubes direct fumes back into the carburetor for safe operation while on rough waters Dual feed fuel inlet with mechanical secondary Classic dichromate finish with center-hung floats and 5 airhorn Calibrated to compensate for unique engine loads found on boats Designed to meet Coast Guard requirements