Mercruiser usually comes with a water seperating fuel filter mounted to the engine, and if you suspect a continual issue with water in the gas tank,it is also a good idea to add one of those type up bu the gas tank, the fiber inside the filter absorbs the moisture, and stops it's flow, and prevents it from entering the carborator.
Gentlemen, it showed up, that i have water in the fuel tank, respectively in the fuel system. Beside my suspicion, that croation gas stations may increase their profit in filling some water into their circuit, i thougt about the unlucky position of the fuel tank air-ventilation-inlet. It might be of a problematic nature, in wavy sea condition. Does anyone have any experience with this? Maybe a water separater could be of use. All the best from the Adriatic Sea