Sydwayz, Didn't you have your ECU's sent in for that free Merc upgrade last year to lean them out alittle to eliminate how rich the early ones ran? Just a guess but I would say that everyone getting alot of soot on the transom also is having the oil darken quickly. Did you have the problem before and did it clean it up after the reflash? I think you had a thread on this a while back?

I just pulled my plugs and they are as lean as they can safely be... I thought the same thing about 3 days after I started this thread. It's just one of those things that really isn't hurting anything but it annoys you when you pay 6.69 per quart.

If there is a re-flash that leans it out, I would certainly not be needing it but I still have the transom soot. got over that a while back...

turnerrd is correct. There is a technical bulletin or whatever from Mercury on the 496s. The early ones were set pretty rich. I got my ECUs replaced under my warranty coverage via this new program. As it turns out, it was better for my ECUs to be replaced vs. re-flashed, and this was Mercury's decision.

It definitely did 'brighten' my transom!

snapontoolsjt, if you contact your local Mercury dealer with your engine SN and the SN of your ECU, they can tell you what you may/may not need done.

black oil
 

hey monstaaa you said that some of the fountains you have worked on have black oil.i too am having the same problem.have changed oil 3 times just this year and still have the same black oil.i am wondering if my oil temp is too hot.it runs about 240.too hot?

It's tough to read plugs on the 496 as it has an individual coil for each cylinder. This makes it burn hotter especially at idle and thats probly where you are checking them so the plugs will never really look fat always lean. Excessive soot on the transom definatly means rich though.
Sydwayz, didn't you recall a couple of guys saing they lost speed and RPM after the reflash? Did you see that with your new ECU's? I'm thinking about sending mine, but thats what stopped me at first.

Rob

I hit my best top speed ever before the ECU's were replaced with the leaner program. The boat had none of my usual gear on it, and was nearly empty on fuel.

I have never tried that again on my boat, and have actually added weight with subwoofers, amps, and other things. I don't go boating to squeeze out an extra .763421C87 mph. I like reliability and longevity, hence my extended warranties until 2010.

I do think a few other folks may have mentioned loosing a few ticks.

I'd have to say the dark oil is caused by a slight rich condition that produces the carbon (black). It's not like it's raw fuel thats getting into the oil. Just not completly combusted. Given the choice to be a little rich or little lean? Not a tough decision. It would be nice if someones whos in the know specifically on the 496 could chime in here.

Ran into a 496 torn apart this morning. noticed that the drain hose (port side) and the dipstick tube (starboard) are in relatively the same center location of the oil pan on their respective sides. called mercury to ask about recomended way to remove the "most" oil from this particular engine.

as I orginally assumed, they are both equal. they are both physically located at same depth in pan etc... they both remove the same amount of oil.

after carefully looking at the overall picture, one would actually leave MORE oil in the pan by raising the bow of the boat in the air much past level state. however, if this is done, it would net a very minor residual drip drip overnight as some have suggested. either way this is not the issue.

how are you changing your oil? and what is your procedure. and 240 is hot but not too hot, unless your reading is wrong or it contaminated