Where do I install a temp gauge sensor on a 2006 60 hp merc 4 stroke big foot . Thanks John

Probably need to replace the spring. Contact a Merc dealer for parts and support.

Follow blue wire and see how is connected. Sometimes dash lights are connected to nav lights.

Sounds like the temperature gauge or temperature sensor is faulty and giving a wrong reading. Too high of an engine temperature will shut that engine down. Check the temperature with a temp gun if you can get one to see how hot it is before it shuts down. Aim it at the coolant line or the engine block. Or take the temperature sensor out and check it by putting it in a pot full of hot water with a temperature gauge and boil the water to see how high the temperature gets before the sensor closes or opens. Use an ohm meter across the sensor terminals to know when it's either opened or closed. Some of these are set up to operate in either open or close mode.

Red is Battery +
Red/purple is ignition
Yellow/red is startermotor
Black/yellow is motor kill
Black is ground

To have ignition, black/yellow wire must be disconnected
On is red/purple on bat+
To start Yellow/red on batt+
To kill: black/yellow on ground

I have a 25 hp merc outboard that starts right up but idles high then low and when running it just dies . Is it a choke problem?

that depends upon which engine you have. if its the quad 4 its located on the drivers side behind the head.

the big brain

I couldnt find one anywhere for my merc 75hp 2stroke-ended up buying a service manual $70

if i disconect temp sensor fans come on cool engine but then no temp gauge

That's what I'd expect after unplugging.
This is sounding like a bad coolant temp sensor. Test it or replace it before you do anything else. Read this post on how to test an engine coolant temperature sensor

Test engine coolant temperature sensor Ricks Free Auto Repair Advice

Any cooling system fault in JULY/AUGUST is a big deal. This sensor is 22$ and can be installed in a COLD engine in minutes.Very small cost for accurate gauge so you can monitor gauge and know if real overheating conditions exist.I would probably spring for a new thermostat while Im servicing that sensor and coolant just for good measure. stay cool