I have a 2005 280 SeaRay with the 8.1 merc engine. I've been having issues with the engine temp gauge fluctuating while on plane. Both the digital smartcraft gauge and the analog gauges swing from a normal operating temp to the gauge limit within a matter of seconds. This only seems to happen with the motor in gear at planing rpms. I can run it all day long in neutral in the slip with no problems. Only when I try to go up on plane do I start having problems and then of course the guardian system kicks in and cuts the throttle. I've tried unplugging/plugging connectors on the engine but no luck. Any ideas on what might cause a gauge to do this? I'm 100% sure that my engine is not overheating, but the smartcraft thinks it is, therefore I'm screwed.
