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2009 Mercury Optimax Idle / Low RPM Issues

P

Psyk

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Any Ideas ? I've got a bad kick / hunt every few seconds at idle / low rpms and sometimes it stalls but seems to work okay higher rpms. I've got about 110psi fuel pressure, 95psi air pressure. 25psi low fuel pressure. Compression tested same all 3 cylinders, coil pack gap tested at 10mm and each are okay, brand new plugs are gapped around 0.030. The Fuel Diaphragm was inspected and doesn't have any holes or cuts in it. It's a 2009 Optimax 115hp DFI. Haven't been able to run the boat properly since I bought it.

Running out of ideas, any help would be greatly appreciated, thanks đź‘Ť.
 
Last edited:
Sorry, in my old age I replied to a text while multi-tasking & as you can see I got it wrong.

Regarding your issue, and I'm no Opti expert but I'd look for a dirty injector. It's probably acting up at higher RPM also but not as perceivable.
 
Yeah that's what I was thinking, do you know the best way to test them without bringing it to a dealership? Can you physically see problems with them or are they usually only found while spraying? Thanks again!
 
Well if you could isolate it which cylinder then it would be easy...

Another idea, take a fuel sample from the fuel rail (from the Schrader valve). Look for any water contamination. A periodic drop of water will do it too.
 
Yeah I took a fuel sample from the VST port and it seemed to be okay without any water. Unfortunately I can't isolate any of the cylinders because the engine dies as soon as I do.
 
Another thing I forgot to mention was that when I'm finished with my high pressure test the air drops fairly quickly to 0psi while the fuel pressure stays about 10psi.
 
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