The collision took place at 2.15am and the car failed to stop at the scene.
The man from West Lulworth was admitted to hospital with serious injuries and he needed what police are are calling a surgical procedure.
Anyone with information about the identity of the driver at the time of the incident should contact the Weymouth Traffic Department on 101,quoting incident number 321 of the 3rd August.
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Showers soon dying out this evening to give a dry night with some long clear spells and light winds.