Go Back  Offshoreonly.com > General Discussion > General Boating Discussion
I am concerned...motor issue? >

I am concerned...motor issue?

Like Tree0Likes

I am concerned...motor issue?


Old 07-09-2006, 10:39 PM
Thread Starter
Join Date: May 2004
Location: Midlothian, VA
My Boat: Boatless :(
Posts: 615
Default I am concerned...motor issue?

I have a 496HO. When I start it for first time in a 24 hour period, all is fine. However, when I run her and retart her within an hour of the last run, I get this black smudge from my exhaust pipes (I have rubber flaps to prevent water from backflowing in if this matters). It is a bit hard to explain - will get a pic however looks like a combination of oil and soot that just sits on the top of the water. At times, it is excessive, making a line about 1" wide across the entire width of the back of my boat.

Any ideas?

Last edited by Ca$hed Out; 07-09-2006 at 10:43 PM.
Ca$hed Out is offline  
Reply With Quote
Old 07-09-2006, 10:43 PM
GOODT's Avatar
Join Date: Apr 2005
Posts: 2,675
Default Re: I am concerned...motor issue?

merc calls this trailering effect it is common on boats with intergrated swim platforms they do have a current reprogram bulleten on it but still does it but the update does help a little
GOODT is offline  
Reply With Quote
Old 07-09-2006, 11:53 PM
Forum Regulator
VIP Member
iTrader: (1)
Sydwayz's Avatar
Join Date: May 2001
Location: Worldwide
My Boat: 17' Speedliner Cat & O.P.B.
Posts: 22,508
Default Re: I am concerned...motor issue?

Shawn, do you have Captain's Call or Corsa Switchable exhaust? Sounds like the bit of water that sits in the tubes after you run for a bit dissolves some of the soot inside the exhaust, and oozes it out when you are bobbing.

Get ahold of a Merc Dealer and run your ECU's serial number through the system. There have been about 5600 different reprograms for the 496s. I had mine reprogrammed via a ECU swapout, and mine leaned out a bit and gained a little fuel economy; much less transom soot as well.
Sydwayz is offline  
Reply With Quote
Old 07-10-2006, 07:20 AM
Platinum Member
Platinum Member
CigDaze's Avatar
Join Date: Jun 2001
Location: St. Petersburg, FL
My Boat: Cigarette 35 Cafe Racer
Posts: 21,346
Default Re: I am concerned...motor issue?

Newer Merc's like the 496HO run quite rich in their stock form. There is a bulletin on this soot, and I think all they do is reprogram the ECM to eliminate it. My Baja with the 496 would do the same thing - after a day out, my transom would be covered in soot.
CigDaze is offline  
Reply With Quote
Old 07-10-2006, 08:57 AM
Join Date: Sep 2005
Location: spring lake, mi
Posts: 0
Default Re: I am concerned...motor issue?

More then likely they have to much startup enrichment in the higher coolant temperture tables. Common on cammed GM cars and trucks too, I usually adress that in the warm startup enrichment tables by taking away some fuel. I am sure they adressing it in the same way with the new flash.
hellbents10 is offline  
Reply With Quote
Old 07-10-2006, 06:34 PM
Join Date: Jan 2004
Location: San Diego, California
Posts: 2,777
Wink Re: I am concerned...motor issue?

Another thing to keep in mind here. Stock 496Mag's and HO's are setup to run on 87 octane fuel. If you run them on 91 octane or higher you are actually slowing down the burn and losing a little power which will increase the soot you are describing and cost you some power.

Ray @ Raylar
Raylar is offline  
Reply With Quote
Related Topics
Thread Starter
Last Post
07-05-2007 09:11 PM
General Q & A
07-21-2005 04:35 PM
08-24-2002 10:58 PM
Erie Desire
General Boating Discussion
01-21-2002 08:24 PM

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

Quick Reply: I am concerned...motor issue?

OSO Sponsor
OSO Advertiser
OSO Advertiser
OSO Advertiser