I've got a 2001 Merc 75HP on a 16.5ft Ranieri Azzura which has run fine for 2 years. Last service of the engine they took off the prop and alledgedly put same one back on. Now above about 2000rpm if your not holding wheel tight boat swerves violently to starboard i.e. direction of prop rotation. Servicer can't figure it out what's changed. Anyone?