A marine pipeline installation vessel for laying a pipeline on the seabed, said vessel at least being adapted to carry out the reel lay method, wherein the vessel comprises: at least a first and a second storage reel for storage of the pipeline to be laid, which storage reels are positioned in or onto the vessel; a pipeline launch tower mounted to the vessel, which pipeline launch tower is adapted to launch the pipeline in a firing line along said tower; a pipeline guide which is mounted at an elevated position to the pipeline launch tower, which pipeline guide has a pipeline guide surface member providing an essentially circular or semi-circular pipeline guide surface, which pipeline guide is adapted to - in a primary pipelaying position thereof relative to the tower - guide a pipeline from a first storage reel over the pipeline guide into the firing line, wherein said pipeline contacts the pipeline guide surface at a first contact point fore of the firing line and departs said surface at a first departure point into the firing line.