07 496 HO boat with 120 hours- continues to have knock sensor reading and restards motor-new knock sensors and now mecahnic says that its the computer program and is to sensitive-he tried a new Merc updated program but still not solving the issue-says they will try a whipple program $700 and if that does nt worka new computer $2000- does this sound correct? I use the boat little and has been in shop 4 times same issue-in shop now for 1.5 months