A friend has owned this boat for approx 3-4 yrs. The boat has C18 Cats 700hp ea and about two months ago it would not get up on plane. Its a relatively slow boat and when on plane about 14 knts. Bob from Cat came over about a month ago and said its not an engine problem it was likely props. Thats when owner had boat pulled and all the bottom work done. The bottom was painted, new cutlass bearings, props pulled & scanned by General Prop, rudder and trim tabs both check okay. Put back in water and still same problem. The engines will get up to 2200+rpm and boat will be struggling trying to get on plane. Any ideas on what the issue could be.