2012 204fsx mercury 4.3 alpha gen ii temp gauge

[2012 204fsx mercury 4.3 alpha gen ii temp gauge]

Thanks Kelly! I appreciate your response and look forward to your reply. 
My temp alarm is not sounding off so I am not over heating. 

Have a great day!

[2012 204fsx mercury 4.3 alpha gen ii temp gauge]

Well the temp gauge drops to 100 degrees when running over 3000 Rpm. When I slow down and just cruise it pops back up to around 160 degrees.  Any idea what’s going on?

[2012 204fsx mercury 4.3 alpha gen ii temp gauge]

Just purchased this used 204fsx. 204 hrs. Runs amazing. Just noticed that the cooling temp gauge is not working. Worked the other day. What should I check? I’m pretty tech savvy so should be able to trouble shoot with your help. 
merc 4.3L is not getting hot. Exhaust is cool to the touch...  hope someone can shed some light. First step I’m thinking is to check the temp sender wire. But not sure where it is?  
thanks all. 
happy boating