A boat drive including combustion engine located within the hull and a drive unit located outside the hull. The drive has a propeller shaft and an exhaust system with an exhaust duct and an outlet. The exhaust duct connects the engine to the exhaust outlet for carrying away exhaust gases from the engine and cooling water introduced into the exhaust duct. The exhaust outlet is arranged in the propeller shaft. A first exhaust release opening is arranged in the exhaust duct, between the engine and the exhaust outlet, so that during operation, a first fraction of the exhaust gases and cooling water is discharged through the first exhaust release opening, while a second fraction of the exhaust gases and the cooling water is discharged through the exhaust outlet. A device is provided for adjusting the first fraction that can be discharged through the first exhaust release opening.