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As Phil said your going to have to isolate the problem. If it is in the cable or helm, grease may help but it's probably rusted and one or the other or both need replacing (cable probably). If it is on the motor end check the bushing that (not sure of the name) push/pull end of the cable goes through clean/rusted. Check grease fittings on the pivot shaft located just below the belly pan of the motor could be 2, one at top and one at bottom.