What is the length of the fuel sending unit for the R 31? I believe I need to replace the Rochester 9800 fuel sending unit as the Volvo and Garmin panels always indicate zero fuel. Checked the electrical connections and they are not corroded. The only other number on it is 150-3514 but that hasn't helped in ordering the correct unit. I would take it out and measure it but I currently keep the boat two and a half hours away. Thanks!