My port side engine drops rpm and dies slowly when I shift into forward, 90 fountain twin carved 509 with bravo drives imco uppers. Happens to one side only! Any help suggestions would be greatly appreciated.

I have a friend who had this same issue earlier this year on one motor. His ended up being a bad fuel pump. Not sure if that is the same in your case, but its very easy to diagnose.

if its EFI ID start with the IAC

I’ll guess carved = carbed ?
New problem ? Was it running fine all this summer and then this showed up ?

What have you checked thus far ? Do you know how to check timing and clean out the carb ? Check/replace spark plugs ? Etc, etc ?

probably so SB, I didn't know what a carved 509 was

yes carbed motors, I just bought the boat and got her on the water yesterday. Timing was set few days ago by a local reputable shop. Boat sat for over two years prior.

carbed lol, sorry auto correct

Plugs, new msd coils, timing set, new water separators all replaced.

has electric pumps. Pressure is same on boat motors looking at the gauges

did you pump out all the old fuel ? Id think those carbs would need a bebuild with old gas setting in them for 2 yrs