496 HO Running too Rich

[Rob Franck]

Have a 05 496 HO all stock in my boat and it has been running really rich. I can smell raw fuel coming out the exhaust. Had the boat in for service at a reputable co. And they say nothing comes up on the computer scan. Any suggestions?

 

[Done-it-again]

You running 87 or 91?

 

[SBMech]

Is it missing or is it just richer than normal?

 

[02HoWaRd26]

Go get some new plugs, it’s not a hard motor to do new plugs NGK TR5iX #7397, they come gapped at .040 take and very gently regap to a .050 and install.
I would bet you have a few dirty plugs and these seem to be the best ones for the 496’s. These motors seem to go through plugs way way faster than others so it’s not a bad thing to do and i would bet it solves the issue

 

[HitIt]

You running 87 or 91?

Yep. More octane is not more better

 

[Runs2rch]

Go get some new plugs, it’s not a hard motor to do new plugs NGK TR5iX #7397, they come gapped at .040 take and very gently regap to a .050 and install.
I would bet you have a few dirty plugs and these seem to be the best ones for the 496’s. These motors seem to go through plugs way way faster than others so it’s not a bad thing to do and i would bet it solves the issue

Tr55Ix is what you want. They come gapped at .055 a little anti seize and install. Factory Gap is .060.

 

[02HoWaRd26]

Tr55Ix is what you want. They come gapped at .055 a little anti seize and install. Factory Gap is .060.

I’ve used those as well, the 55 is actually a 60 i believe tho. And always easier to gap than to compress, i left the 55’s alone on mine then went to the 5’s and called to .050 and wouldn’t say i noticed a real difference but it did seem to sound a little more crisp.

 

[W.O.T. Marine]

Check your fuel pressure. The fuel module caps have paint issues that plug the regulator. Pull and inspect both the cap and regulator. May not be your issue but check this regardless very common issue.


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[Lavey 29]

Most likely he has the GEN 2 cool fuel being a 2005. Very late 2005 the 496 changed over to the Gen 3 cool fuel. But it all goes by engine serial number. With that said the GEN 2 cool fuel system never suffered with any paint issues. GEN 3 cool fuel it is very common for paint internally will peel away and even ball up in the fuel injectors. I know first hand cause I flow test and clean fuel injectors daily.

I would fuel pressure test ( 40 to 44 psi very steady is what you want. Also check all ignition components out very well. Do not gap the NGK TR55IX they come pre gapped at .060. That is the gap needed. Its a fine wire and gapping them can bend the fine wire depending how one gaps plugs. Scan the engine and by someone who knows how to read the scan and knowing the correct parameters for PCM 555. Look at coolant temp and MAP parameters during the scan. I am sure new plugs and quality spark plug wires will always make a 14 year boat run better.