Re: Cooling problem solved now what's wrong with my tach?
On our boat the tach is energized when oil pressure detected by the oil pressure alarm sensor. Check the loose wire may have been connected to one of the oil pressure senders. Sea Dragon, Westerbeke W40, has two oil pressure senders. One which closes an electric circuit when oil pressure is sensed (this is a way of identifying whether the engine is running or not – this is used to activate the hour meter which is part of our tach along with other "things") the other reads oil pressure for the oil pressure meter.
This may or may not help.