From a engineering pov. Engines should be fresh water washed everyday if operating in a salt water enviroment. I would have also thought asking your engineers would be the first step not posting on the internet (although I know the answers to all lifes problems can be solved online
)
If the engine is failing by a large margin and you are aware of that its more an engineering matter. However I would revise your SOP's and start washing everyday, I previously worked for a company where all our engines reached overhaul with no problems, Turbomeca believe this was partly due to our washing routine.
HTH