Temperature gauge connections on perkins 4-108

My temperature gauge is not registering. When checking the engine compartment I notice the wire connected at the rear top of the 4-108 engine was not connected to any other part of the engine. To what part of the engine is the wire to be connected?

Also I have a similar problem with my tachometer, as it is not registering any rpm. What are the connections on the engine for the tach?

Any info/advice would be greatly appreciated. FYI ,The engine is in a 1976 Choy Lee Ketch.

Thanks,
deni

Pictures help. The are many variations of the 4108. My 4108 (running a generator, and from the early 1970s) has the temp sending unit at the front of the head, yours could be at the back, I know there's a plugged hole there. You should have or acquire a wiring diagram. Basic gauge wiring has a 12 volt and a ground connection usually daisy chained together to each gauge. Power supplied thru the key switch. The temp gauge has a wire running to the sensor. The tach to either the alternator or a sending unit. 1st I would undo each connection and clean any corrosion, then trace the wires between the non-working gauges and their senders.
The engine isn't electric, but many of the accessories are. No wire runs from one part of the engine to another part of the engine. For help you need a much better description.
A prior owner could have replaced the stock alternator with something else. I did. That would change the tach connection.
Find out what the loose wire is connected to and what alternator you have and if individual wires or a plug connect it.