Well the boat's out of the water and had its service.
More recently, the engine was only revving to 4800 rather than over 5000 and the top speed down to 34mph! With engine still racing at idle.
Evidently though, unlike the general forum consensus of it being the TPS, an alternator bolt had snapped. Quite how, i have no idea, the cowling hasn't been off and nothing has been hit all year. ABC marine in Anglesey who did the service have said that it now runs fine. They also alluded to coming across the problem before on the V6 optis. Seems strange.
Anyone else had this?