Officials with the Washington State Department of Transportation Ferries Division said that changes to software controlling the propeller system on the new Chetzemoka ferry may provide a temporary solution to vibration issues first discovered last month. Additional sea trials are scheduled for the middle of next week after representatives of the propulsion-control company write software exerting greater control over the engine “ramping,” which allows the bow propeller to slow the ship as it approaches the dock. The goal is to ramp up the propeller speed over a period of a few seconds longer, as opposed to a more sudden and quick thrust of power.