Hello All.
So before I bought the boat I have not the old owner replaced the gauges.
The temp gauge is always peged at 240 degrees.when the key is off and batteries off.. still peged.. when I turn the key and start the boat.. gauge does not work..needle dosent move..

Could something be wrong with the gauge.. the temp sensor in the intake does a have a wire going to it.. and as far as I can see the gauge looks to be wired...
any ideas..

May not be the correct sender for the guage. Take the wire off of the sender and see if the guage zero's out.

If the gauge is pegged when there is power going to it, either the wire or sender is grounded.
Spazboz is correct. Disconnect the sender wire. If the gauge goes back to zero with power going to it, the sender or wire is grounded. If it stays pegged and the wires are hooked-up correctly, the gauge itself is defective.