I now have 3 ways to determine speed on the boat-- wheel paddle for water speed on Lowrance, GPS for ground speed on Lowrance and Vac line from dash speedometer. I bought a pilot tube and connected it to the vac line and am about 10MPH under the other 2 devices. Am curious about trying to get it to work since I saw a schematic of the Lower Unit showed a "Speedometer fitting" on the front side of the unit. This fitting now has a rubber plug covering it. Does anyone know if the vac line would be better connected to the lower unit or pilot tube?<br /><br />Thanks in advance for any advice.
