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