I have 2006 35' Baja Outlaw with 496 HO's with 280 hours. Motors have CMI E-Top Headers with factor quick/quiet option. Exhaust Tips are 4' off rear of boat. I am a new powerboat owner, and was wanting if it is normal to get black exhaust dust on every hard run that is made. I can clean the entire rear section of the boat, exhaust tips and swim platform entirely and after one short trip up the lake the tips are covered in black dust. IS this normal for big powerboats?

DO I have a motor issue or is the black dust normal for my situation?

Thanks Mike

http://www.offshoreonly.com/forums/v...nsom-soot.html

One of many threads but that one is pretty involved

Scan the engine - MAP sensor parameters and coolant temp sensor parameters. Make sure your coolant temp is at the correct degrees while idling and running. 160 to 170 is normal for these apps. Any lower and it will be pig rich.

Change your spark plugs and check wires - Test wires with a ohm meter

87 octane fuel

CLEAN your flame arrestor deep clean it. This always helps. The 496 Flame Arrestor holds alot of grime and belt dust.

Possible intake gaskets bad. 1 st gen GM intake gaskets were very poor and thin - 2 nd Gen gaskets a world of difference.

Call merc to see if your PCM needs to be recaled and or if you have the latest recal already - have your engine serial number ready and all the numbers on the PCM to pass on to them.

Thanks for the info. Are you saying that 87 octane is bad to use?

NO all Merc black engines are calibrated to run on 87 octane fuel. that is fresh 87 octane fuel AND without 10 cans of sea foam in it either.

Scan the engine to see your temps as sometimes dash temp gauge can be off and way off. Just had a Baja Outlaw with a 496 showing 125 degrees on the dash gauge but scan tool showed 159 thru 162 degrees after running for a while. I knew the dash gauge was off by feeling the engine / T stat area, so hence hook up the scan tool to monitor it.

The Merc Black scorpion engine needed a higher octane fuel for that stock app FYI for whomever.

1) Most of the 496s had a reprogram while under factory warranty/service to reduce transom soot. Speak to your local dealer to make sure this was done to your engines, by referencing serial numbers in their system.

2) You have changed the "combination" to your "pump". An engine is a pump, and it has to be calibrated correctly for the goes-in-ta & goes-out-ta.
Since your engines do not have the factory exhaust, I would be a little suspect of your PCM calibrations.
Were they adjusted when the headers were put on to compensate for the new exhaust?
Were they never reprogrammed per topic #1.

Operating temperature is very important. Are you running in really cold water? This will make it a bit harder for your engines to heat up, also resulting in excessive exhaust soot.

Exhaust soot and 496HOs is not a new problem. As I mentioned, it's actually and old problem and most of them had the kinks worked out with a factory reflash or entire PCM replacement back in the day.


Also, I assume you mean your exhaust tips are 4" (2 ticks means inches) past the transom of the boat.
And not 4' (1 tick means feet) past the transom. If the latter is the case, we need to see a picture of your horizontal smoke stacks
You may actually be rolling coal, the hard way.

I called merc with my serial numbers and PCM numbers and they said that I had to take it to a Merc dealer and have them call. Do you have a connection there or something?

As you see above -- there is quite a bit involved in this question an solution. I can say that when I swapped the stock flame arrestor / air filter on my 496HO with a K&N, this helped alleviate my transom soot condition quite a bit.

I had a similar issue with our 2001 Baja with a 496 Mag. I was told by the dealer that I needed to have the PCM updated to access smartcraft data (which was incorrect). When I got the PCM back I had noticeably less soot on the transom. Not totally gone, but almost so. The bad news? I lost 4 mph on a boat that was not that fast to begin with (62 to 58). The reflash is free and was part of a service bulletin, but it does have to be performed by a dealer (including removing and reinstalling the PCM).