496 HO running rich?
 

I have a 09 22 Classic with the 496HO (with 200 hours) and I get black/dark residue on the stern and Corsa exhaust tips. New plugs were installed at 100 hours and 2 years ago the marina checked the motor with the Merc computer and nothing was found? Any ideas on how to get this sorted? And I don't have a oil consumption issue, thanks

Have Whipple reprogram the ECU. There was actually an update by Merc to fix this but I doubt they will do it anymore - enter Whipple. I think its like $800

Make sure to only run 87 octane as higher octane gas can soot the transom as well as the early programming issue.

Check your Battery.... they are very sensitive to low batteries....low amperage puts them in guardian mode....

What did the old plugs look like when you replaced them, what do the new ones look like now ? cold be warm up enrichment, water or air temp.

Yep we have good stuff here on the lake (Valvtech or 90 octane rec gas) so I'm good there

We're good there too.

The boat starts up easy, hops out of the hole fast, and goes 75 plus so I'm guessing the plugs are fine. I'll pull the plugs and check them out but since peeps are talking about an old issue with ECU I'm going to get it reflashed this winter. Thanks to all

If the plugs are clean, you're not running rich, could just be the nature of the beast. Good luck

09 should have the latest calibration

IS the software level listed on PCM, if so what would it be for updated? Or when I check with scanner?

Might just be sooting up during idle, if so, then may be the MAP. Check the reading

Huh, missed the year. ‘09 shouldn’t have that issue as even my ‘03 had the updated programming from Merc. It would only soot a very small amount in the spring when water and air temps were cold. Otherwise no soot at all.

Is this sooty transom a new issue? Running 90 octane on a stock HO is alot of your problem. If it's an 09 HO you have the updated PCM fuel table. No reason to mess with that. If it's a new issue I would comfirm fuel pressure at rail. Should be 42-3psi KOEO. If higher, look into your fuel system contaminated from paint from the Gen 3 cool fuel box. It restricts the regulator, injectors, pump screen pickup and can cause fuel psi to spike and overfueling is result.

Early 496HOs did have either a reprogram from Mercury or a whole ECM replacement, which helped with the sooting issues.
Ensure that your ECMs have the latest software update by talking to your Mercury dealer.

The colder it is, the more they soot. Spring and Fall were worse than hot summer months.
Mine ran the cleanest on 87 octane. Anything else sooted the transom noticeably more.

I'll again emphasize run good quality 87 octane only. Higher octane will soot and is a waste of money on that motor in stock form. I run Shell 87 and have zero soot on the transom. I had to slum it one weekend and put marina 91 and had soot, not kidding.

did mercury publish a bulletin, if so what's the number?

Same here, mine had a little soot when the water was cold. Ran plain old 87 pump gas in mine. Ran great! Mine was a 2005 model.