Ok guys my buddy needs help with some trouble shooting. Between me, him, our boat mechanic, a few other local mechanics we know, and even people from Mercury that our mechanic talk too this problem doesn’t seem to be one that’s so common. First and foremost the motor is a 2008 250 pro xs. I will also state he’s had the boat a year with no engine trouble and the motor ran fine right up to the point of the problem. Here’s the whole run down. We went out on the lake. The engine crunk and ran fine 3 times in a row, then at the last spot we fished the motor would turn over but not start. While on the water we checked the kill switch multiple times, swapped batteries, made sure there was fuel and air pressure. Everything seemed to be good but trying to crank the voltage gauge was reading lower than normal and the motor only seemed to try and hit as you were letting off the key. We got a tow in and went straight to our mechanic. He has done everything possible. He found that the voltage was dropping below 10 volts which is not allowing the computer to read to start the engine, but we can’t find the source of the problem. He completely disconnected the harness on the boat side and ruled that out, checked all the relays, all the fuses along with the fuse holders, all the grounds have been checked (including the rubber coating that has been known to cause problems), tried another crankshaft position sensor, tried another starter to make sure it wasn’t pulling the voltage down, checked the alternator, all the battery connections, double checked the compressor, made sure there was fuel pressure, and the motor is getting spark but only as you let off the key. When you turn the key on the fuel pump engages but the injectors never fire because while cranking it drops below 10 volts which is not enough for the computer. As I said before the mechanic has consulted with many friends in the business as well as mercury people, and we have both talked to other mechanics and nobody has seemed to run across this same issue. We’ve known our mechanic a long time and we trust his knowledge. I would consider him one of the best in our area its just a problem that he hasn’t encountered as well as those we’ve talked too. He’s thinking it’s a problem in the main harness on the engine now and we’ve got an extra harness we’re going to try in the morning to see if that changes anything. Can anyone offer any suggestions I haven’t listed or any other insight that might be helpful?
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