280 Mercury cutting out at 4000 RPM

[John#24]

Hi

My 280 is cutting out above 4000 RPM

The engine runs and starts ok
When it cuts out it is a full cut the fuel relays are cut the supply to the coils is also cut
When in the water the engine will fire again when running down The ignition goes through its test cycle ( The overheat buzzer comes on when the ignition cycles just like when you first turn the key on )
We have changed ECM ( With a second hand one that came of a running engine )
We have changed crank angle sensor ( Second hand history unknown ) A new crank angle sensor is arriving overnight
TPS tests ok and was changed out as was the MAP sensor
We have plugged a new remote to eliminate the OEM control box key switch and harness

This engine had a fuel pressure problem at Christmas and the fuel regulator was replaced and it ran fine after that for the 2 weeks of our Christmas break

The next time it was taken out the 4000 rpm cut fault started ( Then NZ locked down and boating wasn't allowed ) Then winter I drained the fuel out over the winter I have replaced the Fuel filter and it now has fresh fuel

This 4000 RPM cut out is consistent and acts the same as turning the Key off

This is driving me nuts

Any ideas

Cheers John

[John#24]

Hi

Just a update Make sure when replacing plugs use BPZ as soon as I replaced the plugs with resistor the problem went away
The funny thing is we had done 3 days on the wrong plugs without problems ( In saying that we were only running at low revs )
The correct plugs solved the problem
We had a previous problem when the fuel pressure regulator flooded the engine we went to the local marine shop and were sold the non resistor plugs We replaced the plugs and then figured it was the pressure regulator Replaced the regulator and left the new wrong plugs in it

Its sorted now

Lets go racing

Cheers

John