The mechanical oar system is a manually powered propulsion system for a vessel. The vessel is a personal watercraft. The mechanical oar system is configured for use with a person. The mechanical oar system is powered by the person. The mechanical oar system comprises a plurality of drive mechanisms and a vessel. The plurality of drive mechanisms are integrated into the vessel. Each of the plurality of drive mechanisms is manually powered. Each of the plurality of drive mechanisms comprises a mechanism that moves an oar structure (referred to in this disclosure as a blade). The oar structure propels the vessel in a desired direction. Each of the plurality of drive mechanisms is oriented relative to the vessel such that the direction of the propulsive forces can be adjusted by the person.