oskoloudik
New member
HI. I have a 2012 Merc 60efi bigfoot with apex 100 hrs. I have been chasing this problem for the last few years. Ready to give up and take it to the dealer but want to give it one more try. The issue is that the engine starts losing fuel pressure after running for a few minutes the first time in the day, it's very inconsistent with time intervals, 5 min- 20 min. I can run it wot or half for a bit, then I start losing fuel pressure and I have to throttle down quickly and idle around, I notice the fuel pressure is back up 42psi. After that I can only throttle up for a few seconds and the process starts up again. The next day the same thing, good for 5 - 20 min, then back to idle. I have no warning chirps/horn sounds to indicate an issue. To date I have cleaned out fuel lines, replaced low/high pressure filters, replaced low pressure fuel pump and high pressure pump. Run fuel directly from the fuel canister to the first fuel filter, bypassing the boat fuel tank. Cleaned out VST. No change. Next I got the vessel view adapter to see if I can see anything. My boat has no gauges, only speed and battery. No fault codes were present upon running the vessel view app. Upon running I paid attention to the temperature reading and noticed that the engine was losing fuel pressure when I hit the 116 f/ 47c and up, back to idle temp went down then I could power up again until I hit those temperatures. Never got an overheating fault code or beeps. This past week I checked the thermostat in boiling water and it opened up around 120f, no blockage, checked the strainer and it was clean. Removed gear case and replaced impeller, and seal face. Old seal face was torn. Back on the water and looked to be good, temperature was steady at 113f/45c for a while then shot up to 116f/47c and that was it back to square one. Re-checked the impeller and seal face to make sure it was installed correctly and not shredded and everything looked fine. That's where I’m at. It looks like it’s going to safe mode and cutting fuel pressure, but I get no warning beeps or fault codes. Also it has gotten progressively worse over the past few years. First year I noticed it only at wot, I could run up to ¾ power no problem. My Last attempt will be to run without a thermostat and maybe unplug the temperature sensor and see what happens while monitoring with infrared heat sensor. Thanks for any help or suggestions.