I have been having trouble with my engine dying at high RPM under load ever since I purchased my boat 2 years ago. 1994 4.3LX Mercruiser I/O carbed with electric fuel pump. It runs great in the driveway, I just set the timing, it was off by 12 degrees!!!! It has more power than ever 
. To diagnose the problem, i put a clear vinyl line between the pump and carb and can see there is a surge of air bubbles if i keep it at 3000 rpm under load in the water for 20seconds or so, then the engine stumbles, i have to back off the throttle a little and the boat starts going again....I checked all my fittings, double clamped all my lines, cant hear or detect an air leak. My question is, could the pump be bad or could it be a carb float issue that can cause air bubbles like that. I will post a video of the problem. I was told to use thicker gauge wire for my pump since it was rigged by the previous owner who also bypassed the oil pressure switch. help pleasee !!! It really sux when I'm trying to water ski.
Boat Engine dies under load high rpm - YouTube
. To diagnose the problem, i put a clear vinyl line between the pump and carb and can see there is a surge of air bubbles if i keep it at 3000 rpm under load in the water for 20seconds or so, then the engine stumbles, i have to back off the throttle a little and the boat starts going again....I checked all my fittings, double clamped all my lines, cant hear or detect an air leak. My question is, could the pump be bad or could it be a carb float issue that can cause air bubbles like that. I will post a video of the problem. I was told to use thicker gauge wire for my pump since it was rigged by the previous owner who also bypassed the oil pressure switch. help pleasee !!! It really sux when I'm trying to water ski. Boat Engine dies under load high rpm - YouTube
