04-23-2021, 12:39 PM
On the last fishing trip last year my always reliable Mercury Verado started missing badly and then wouldn't start except when it was cold and had sat overnight. Ended up only using the trolling motor to do everything. Went home and did testing and found gas in the oil, a possibly bad coil, and a weak battery. So I replaced the coil, all of the filters, plugs and the oil. Started it up and it seemed to be working. Before our latest trip I bought a new AGM battery and headed out. We launched the boat and the problem came back even worse than before. So another trip using just the trolling motor (which can get exciting loading it onto the trailer in the wind). After more testing of sensors and everything else I could find to try I finally found the problem. It turns out these motors have two fuel pumps located in a fuel module on the back of the motor. One motor pulls the fuel from the tank and the other high pressure one feeds the fuel injectors. The fuel injectors need a regulated pressure so there is a regulator in the fuel module. The regulator has an engine vacuum line to adjust the pressure under a load and this line was badly cracked. This made the engine run lean when first started then as soon as the fuel module filled with gas the vacuum line would allow gas to get sucked into the engine causing a very rich condition. So I now have it running as it should and am glad that our first trip wasn't to Flaming Gorge where only using the trolling motor would have sucked. So if you have one of these motors you may want to check the fuel module vacuum line.