Hi all my father in law just broke the temp sensor off in the head of his v8 ski boat. He got all the thread out but the sensor is floating in the head would this cause any overheating problems or would it be ok to leave it in there?

Thanks in advance

The offending bit will probably sit at the lowest point in the head and Not be drawn into the Cooling Plumbing lines, as the flow out is user tapped at the highest point in both Heads.!!   ... If the engine is centre mount i'd think no chance of being a problem, if rear mount (to have the lowest propshaft angle) may depend on Plumbing material ID, 3/4" or 1/2"Copper tube, or Rubber hose if used.!!  ... 2 Water Temp Gauges gives the driver something else to keep an eye on.!!   But this is not the Drivers Prime Responsibility.!!!!
 
Pick a nice day and take it for a run.!!