Merc 115 EFI 2004 ignition Misses

[cxcamp]

I have a 2004 Merc Saltwater EFI, 115 hp. It has been running fine all year, then we were gone and did not run it for 2 weeks. When we came back, it now runs poorly with occasional misfires at idle and worse at higher rpms (above 4000 or so). It almost runs OK between 2k and 4k rpm. I checked fuel filter (clean, no water), plugs (looked good), switched batteries (no change) and oil etc. (all ok).

Any help and/or suggestions are highly appreciated.

cxcamp

 

[Bigjohn1]

Re: Merc 115 EFI 2004 ignition Misses

Even though this might sound counterintutive given the checks you have already made, I recommend installing 4 new plugs and seeing what that does. These engines (although they have very strong reliability record) seem to have plugs that are sensitive to shorting. Don't ask me why but there have been some owners who (after the engine was running just fine) have had your symptoms - changing the plugs cured it. Other than that, ensure the battery is providing full voltage. If neither cure the symptoms, your mechanic will have to begin troubleshooting various electrical components. It is next to impossible to do these checks on your own as you must have the special Mercury adapters to interface between a standard digital multimeter and the individual components.

Cross your fingers and try new plugs and a fully charged battery first

 

[cxcamp]

Re: Merc 115 EFI 2004 ignition Misses

Thanks BigJojhn1, I'll try changing the plugs. The boat has a dual battery setup, and it ran the same with either battery (or both together), so it's hard to see that as a problem.

The daggone plugs are $7 each, too.

Thanks again,

cxcamp

 

[cxcamp]

Re: Merc 115 EFI 2004 ignition Misses

OK, it's working again. I changed the plugs, and also took out most of the gas and added 10 gal o fbrand-new gas with a can of fuel system cleaner. Running normally again.

thanks,

cxcamp