Genset Earthing

If done at all, a marine genset would be grounded/earthed to the vessel's hull. Similarly, mobile equipment would be grounded to its chassis/frame (and possibly to a drag chain).

are you reffering to star connection of generator winding. . normally for marine genset use 3 phase 3 wire and star point is not grounded

if you have a star connected generator you could have its neutral grounded to the vessel or you could use an impedance ground to limit the current entering your generator neutrals in cases of a line-to-ground fault...but, your the size of impedance should be calculated first...