I have a 2009 evinrude h.o 150 Mod. no. E150DHLSEA SER. 05258659 on a 2010 ranger 188vx and I am having a problem with the water pressure gauge. The gauge has not worked sense I bought the boat, the gauge has two wires wires running to it and a black tube that I am assuming water runs to. my question is how should I go about troubleshooting it? should I start at the engine testing the voltage or start at the gauge cluster?