Sorry to say, you guys do NOT know what cold is!!

Dude, I don't know what you're talking about but it was like, chit I don't remember....It must've been like in the 50's or something!!

Tahoe, I understand what you're saying and it is true, but what is there to be done...It's all in the chip and the way it's programmed. I'm still under warranty so even if I wanted to do something about it, I couldn't.

Hi Baja Daze, why not try a ignition box,they clean up a slite rich mixture dont know if you can with waranty. 104 octane boost can also help, more of a compleat burn with that stuff. One more thing might help, a good set of spark plugs.All of the above have helped me in diffrent cases,hope you can use one of the ideas cuz that black soot is a pain in the a$$ to clean and the girls get very up set when its gets on there new little bikinis.

Thanks for the tips Tahoe!
With the ignition box, are you referring to an MSD or something similar.
The 496MAG's already have distributorless electronic ignition which from what I understand puts out quite a good spark. Also, the factory stock spark plugs are premium grade platinum plugs(the equivalent of automotive 100,000 mile plugs).

I'm a little confused about the 104 octane fuel...I thought using higher octane than required will produce MORE soot.

Thanks again!

BajaDaze,
Check out this thread, I've had a constant problem with this, my HP 500EFI's run so rich that my oil was 5.5% fuel diluted after only 18 hours running time. I would highly recommend doing oil analysis with every oil change, it brought this problem to my attention. Also, you may want to have the ECM's reprogrammed, I'm sending mine to Tyler Crockett.
Good Luck,
Paul http://207.55.218.179/cgidir/ubbcgi/...c&f=3&t=003172

Thanks Boathead. Good reading and it seems all too common. Perhaps the 496's are set-up in much the same way.

Mine sooted up until the 10-12 hour mark then went away. Came back again several hours later for one weekend's runnin' then went away again....

Rick

It must be the weather!
...We put a few hours on the boat this weekend in all conditions...Idle, cruise, WOT, cruise...etc, etc.

But I didn't notice too much soot this weekend...It was in the 80's, though!

Seems worst when it's cold

My two cents from what I have seen with the HP500 EFI that I have in the Camaro is that the bulk of the "richness" of the Mercury programming is in the first five minutes of operation as the motor moves towards a reasonable operating temperature. As the motor build temperature (block and oil) the richness clearly decreases and the exhaust "cleans up" - amazing what you can see with dry headers.

From experience in the car and boat - the more you start and stop the more soot on the transom. Keep in mind, the Delco MEFI3 ECU that Mercury uses is an Alpha-N system that calibrates the fuel curve based upon Manifold Vacuum, Throttle Position, and Manifold Temperature. The addition of an O2 sensor could eliminate this problem but would require significant reprogramming. An MSD 6 would certainly help (and I am going to install one here very soon) as the GM HEI ignition just dows not have the jam to completely burn the fuel at cold temperatures (very rich condition).