2003 Sundancer 280 Twin 4.3 Mercuiser engines. I have searched the blogs best I could not sure if there info on this topic. But here is what we have tried so far. Starts and idles fine both engines sound great. we go out to run and it gets up and goes then after about 1 minute at 3000 RPM port engine loses fuel pressure engine just shuts down for lack of fuel. Has new lift pumps spring 2018. We also bypassed the solenoid. Switched around relays for the fuel pump We haven't run on a portable tank yet. I should also mention we removed the filter that separates water out and it was only half full of fuel only. This is located between the lift pump and the high pressure cool fuel pump. Is it possible the cool fuel pump could be bad, do they just die or can they be intermittent? If so is it possible it would allow air back in the line? The lift pump was new last spring. With all that we get it up and going then the Starboard engine seemed to do it as well only when the other engine was running. The Kohler generator ran nonstop so Im not sure if I have a vapor lock or vacuum issue with the tank, but I will try with a portable tank. Sure is funny we would have this happen on both but mainly on the Port Engine. So once it's down, to restart if we cycle the start button to engage the high pressure fuel pump a few times it will then start up and idle forever, it will also run at lower RPM's without issue but when we get going on higher RPM it will go for about a min and the fuel pressure gauge we installed on the rail drops right down to nothing. If I pull the throttles back when this does start to happen it will try to chug away on a rough idle burning up whatever fuel it has and then dies of fuel exhausting. I have only check the fuel/water separator filter one time and it was half full with air and fuel. Last year when I had this same issue on the same engine we replaced the lift pump and it solved it. Could the high pressure fuel pump be weak and causing the lift pump to have issues? IAC have been replaced as well but seems they can go bad not sure if this is related. The fuel is from July 2018 with stabilizer in it. We were down for a rusted through head. It's been a bad 6 months. Boat mechanics are in high demand.