Engine surges at higher rpms

[Lema19]

I have a 115 ficht engine 2001 with 565 hrs. Recently had the EMM rebuilt due to a overheating problem. After reinstalling the EMM had the timing checked; all fine. However, now am experiencing surging problems at 3500-4000 rpms. Engine has new filters and new plugs along with new gas. Also, plugs have been indexed. Checked hard codes and only showing (11), which means system ok; no faults. The coils were also replaced thinking that it may be causing the problem. The lift pump (low pressure pump) was also replaced. Diagnostics performed by mechanic showed no other problems. Does anybody have any suggestions what might be causing these problems?

Thanks in advance-
Lema19

[boats.net]

Print out a engine identification report to see if all injectors match the ones on each cylinder.

[Lema19]

Dear Boats.Net,

The injectors are original to the engine; none have been replaced. Engine running fine up until EEM module overheated. Could this be a problem related to erratic EMM signal to injectors such as a bad ground, loose connection, bad wires? What symptoms could result in no codes?

Thanks!
Lema19

[boats.net]

Was the old EMM sent back to BRP so new one could be programed for your engine? thats when they match it to the injectors that are on your engine.

[Lema19]

The EMM was serviced by DFI Technologies. The regulator was rebuilt and it p***ed the functional test. According to DFI the temperature hit 110 C, which resulted in damage to the EMM. DFI also verified software and calibration and performed a functional retest and certification. Upon putting the EMM back a mechanic verified timing and operation. Diagnostically, the software showed a code of 11, with everything ok. My mechanic even replaced the lift pump, but the surging still exists. The surging or erratic fluctuation in RPMs seem to occur above 3000/3500. Again it's off and on. The tank (external) is good with new bulb. I have over $1500 in repairs and still no solution to my problems. Any further avenues I could try would be most appreciated.

Thanks in advance!
Lema19

[boats.net]

If haven't check fuel pressure then monitor fuel pressure to see if pressure stays steady when engine is surging, also check fuel vacumn to see if have a restriction in fuel delivery to engine(can run on a 6 gallon portable gas tank and hose to see if have problem in boat or on engine).

[Lema19]

Thanks for your input........I have a small 2 gallon tank which I use for winterization. I will try using that and byp***ing the existing tank to see if air is getting through the lines or there is some other type of restriction. Also, as advised, will conduct a fuel system pressure test. Do you advise cleaning the injectors with anything? Is it possible that I may have a constricted injector without giving a code?

Thanks again for the advise
Lema19

[boats.net]

Can clean injectors with Mercury Power Tune or Yamaha Combustion Chamber Cleaner, spray in injector and let soak then blow out with compressed air.