Propulsion system for a vessel

A propulsion system for a vessel, said vessel having a hull with a midship portion and a stern portion, said propulsion system comprising two propulsion units fixedly mounted to said hull on opposite sides of a centre line of said hull at said stern portion, each of said propulsion units comprising a housing carrying a propeller externally of said housing, said housing further defining an interior volume in which a drive machinery is provided for driving said propeller via a propeller shaft, said interior volume being open to the interior of said hull, said housing further comprising opposite inner and outer sides, said inner side facing said centre line of said hull, said inner and outer side being joined at a bow part of said propulsion unit along a leading edge, and at a stern part of said housing along an upper and lower trailing edge, and at a lower part of said propulsion unit by a closed bottom portion, said propeller shaft being provided at a first distance from said centre line of said hull, and said leading edge being configured such that the distance from any part of said leading edge to said centre line of said hull is larger than said first distance for causing part of the water flowing along said hull to be diverted by said inner side towards said centre line of said hull.