2002 merc optimax 135 hp breaks down under load

[Randy a]

Gentlemen,
I have an 2000 optimax 135hp motor, it has always run great and has 600 hrs on it.
It recently developed a sputter, only under load coming up on plane. At idle it runs great, then as I get around 21-300 rpm it will sputter so it will not go on plane.i had a tech put his laptop on it and it said failed injector, so I sent them to be refurbished and performance tested, they were a litll bad but not real bad. I reinstalled them and it ran great for one hour and did the same thing. But it comes and goes.. I can launch today and it will run excellent all day, tomorrow I can't leave the dock and get up on plane it is very intermittent. The tech thinks it's electrical, but the wiring harness looks fine. The ECM guy told me that the ECM will not be intermittent it would work or not..the only code we are getting is fuel injectors1-6 all seperate codes. It seems odd they would be intermittent if and all send codes at the same time if they were bad.
Fuel is crystal clear, lines seem good,air and fuel pressure is good according to tech.
Any ideas?? Thanks in advance guys. randy

 

[CharlieB]

Re: 2002 merc optimax 135 hp breaks down under load

Electrical gremlins. Un-plug and re-plug every electrical connector on the motor, twice, to make sure all connectors are clean and tight.

Same with every battery cable, both ends, sand lightly until bright. If the contact point is painted or dull bare metal, sand it clean also.

Same with every black ground wire on the motor, disconnect, clean, and re-connect. Poor grounds can make strange intermittent failures.