universal m-18
try this: http://www.marinedieseldirect.com/universal/200157/universal-owners-manual-m-18-specifications.htmlThe sensor or temp sender is noted on the lower picture. it's on the housing between the by-pass hose and the coolant air bleed.google is awesomestill having trouble? Okay, looking at the website's wiring diagram (link below) I see the temp gauge and temp sensor are connected by a tan wire through the harness. #8 on the diagram... just locate the engine side of the harness and follow the tan wire to the sensor. Test the continuity through all connections to the gauge. You can purchase a simple continuity tester, with instructions, from any auto parts store for a few bucks.