Hi I have a 1999 bayliner with a 3.0l merc in it. I cant seem to get a proper reading out of my temp guage. At first I didnt seem to get anything, so I checked the gauge itself. I found there was a loose wire, fixed it, then checked it. Wouldnt go up all the way at first, but after grounding out the wire a few times it worked its way up and now maxs out no problem and seems to move smooth without sticking. I had the boat out for a rip but the temp gauge only is reading 120, and the motor deffiantly should have been up to running temp. Im not exactly sure where to go from here. I understand the next step is either the sending unit, or the thermostat. Which do I check first and how? thanks