Got a 1992 Rinker Fiesta Vee 260 with a Merc Bravo II, 350ci, 5,7L. went to start her up she started to crank then died. Gauges all powered up, Batts are both 12.6V. When I crank it starter just "whirs" ??? Is my starter locked up? I heard it could also be dirty/corroded grounds.?.?