An internal combustion engine for a marine vessel has an exhaust system comprising at least a base storage tank, a buffer tank and a scrubbing unit. The base storage tank has a dosing device for supplying base to the buffer tank through base dosing line. The buffer tank has an alkaline scrubber water supply line effluent which is connected to a prepared scrubbing water influent of the scrubbing unit via a scrubbing water supply line and the buffer tank further comprises a scrubbing water influent. The scrubbing unit further comprises a spent scrubbing water effluent which is connected to the scrubbing water influent through a splitter, and one or more exhaust gas influents from the combustion chamber and a SOx depleted exhaust gas effluent.
