The correct answer is A) Reduce power to stay within limits. If the propulsion marine gas turbine is experiencing excessive full power temperatures, the operator should immediately reduce power to stay within the manufacturer's specified temperature limits. This is the appropriate action to take, as running the engine outside of the recommended temperature range can lead to damage or failure of the turbine components. The other options are not the correct response - water washing or borescoping the engine may be maintenance actions, but they do not address the immediate issue of excessive temperatures. Allowing the engine to continue running at high temperatures until auto shutdown occurs could result in serious damage and should be avoided.