hp500 EFI & black soot
 

I have an hp500 EFI, Running 87 octane and I get alot of black soot on the transom. Does anybody have a soltion for this problem? I heard something about Mercrusier reprogramimg the computer so it runs leaner? I also have heard higher octane makes the soot worse. Any info would be appreciated.

It happens. Yes the reprogram is a valid fix but good luck getting a dealer to go thru the hassle for you. You might try an Arizona Speed & Marine Reprogram for a few more ponies too.

Higher octane will make it worse. So will cold weather.

This has been visited on the Tech Forum before. Try a search over there, and OSO will probably move your post over there too.

The answer to question #3 is yes. #2 I do not know if merc does it but Arizona speed does for the 454/502s and adds an MSD box for "hotter spark" It worked on my boat but I am not sure the cost is really worth it.

Stop burning coal:D

Better to burn rich then lean!

Just add MSD boxes and leave the computers alone. Once you start sending them out to get reprogrammed who knows what you are gonna get back.

I had the same thing on the back of my 390. Call inovations in sarasota fl. I tried az.speed an marine not verey helpfull at all.

Thanx for the info guys I'll try the MSD boxs for now.

I had mine reprogrammed by Arizona Speed & Marine been done 3 times and still lean . he did not try to help me find my problem just richened it up. Not very help full. he does not have any patiences with costumers.Its only money maybe someone else needs the business $$$

Fixing to put the MSD boxes on to clean up the transom.most dealers sell them for 247.00 will find a dealer that will help if there is a prob.not much mark upon them. Hell WD on them is 209.00 .sounds fare.