R.P.M. not steady

Question
I have a six cylinder Perkins Diesel in a 45 foot boat and the R.P.M. increaes and decreases when running at 2000 R.P.M.or more by it"s self. What do you think is causeing this.

Answer
Hello Moe...Thank you for selecting the undersigned to reply to your question.

Although you didn't mention the year of the engine or boat, I'm going to gamble on the possibility both are quite old, and if so, there's a strong likelihood the tachometer is malfunctioning and requires replacement. Best you get it properly checked by a qualified and reliable mechanic.

Safe Boating
Ron