mercury outboard efi, possible water/fuel issue

my friend has a mercury efi outboard i think 115 hp he bought it from a guy that said it sat for like 5 years engine looks brand new it wouldnt run properly so we changed the injectors an hooked up a gas container, it ran smooth for like 20 mins an the when you put the trottle all the way down at around 5500 rmp it conks down like something is clogged then it owuld run fine at around 4500 rpm about 15 minsutes later it died down completely we could only go about 5 mph the whole way home at full throttle it would try to run then die down like something is clogged im thinking maybe there is more water in the fuel some where >? where else can it be ? we changed fuel filter an injector, any suggestins posibly fuel water separator ?

First check fuel pressure at the schrader type valve on the high pressure fuel line to the injectors. The fuel pump should trigger and run for a couple seconds when the key is first turned on, then stay on while running, pressure should remain quite steady and within the range spec'd in the service manual.

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