I have a 2002 Lund with a 115hp Mercury EFI (Rebranded Yamaha I believe) that I noticed was down on power last time I took it out on Fort Peck. While I was there it also died once at the point right after I started it and pushed the throttle to where I can only assume the fueling changes as the exhaust note changes significantly and RPM jumps, I thought nothing of it at the time. I brought the boat home and did the maintenance I had planned to do this fall (fluid and spark plugs). I fired the boat up and ran it to circulate the oil, I gave it throttle and when I hit that same point in the throttle sweep, it died. This is repeatable and it dies at the same spot every time, If I push past that point quickly, I can sometimes keep it from dying but it does idle rough. I thought maybe it was a fuel pressure issue but after testing it, fuel pressure is consistent (right around 40PSI) even when I am able to keep the engine running at higher RPM.
I am trying to think of any other relevant information but I am not terribly familiar with boat motors, I know there are differences in the way the fueling works at the very least and I don't want to go around firing the parts cannon. I am comfortable working on the mechanical stuff, know how to use a multimeter as well and can do diagnostic work on automobiles easily but I am stumped by this and am not sure where to even go from here. I am happy to provide more information if needed. I am unable to find any sort of service documentation like the ford workshop manuals I have used in the past for my pickups.
Thank you in Advance,
Jacob
I am trying to think of any other relevant information but I am not terribly familiar with boat motors, I know there are differences in the way the fueling works at the very least and I don't want to go around firing the parts cannon. I am comfortable working on the mechanical stuff, know how to use a multimeter as well and can do diagnostic work on automobiles easily but I am stumped by this and am not sure where to even go from here. I am happy to provide more information if needed. I am unable to find any sort of service documentation like the ford workshop manuals I have used in the past for my pickups.
Thank you in Advance,
Jacob
