Transom soot
 

Every time I run my 42 Fountain with 525 efi's I am getting a lot of soot on the transom. Seems to be worse in the cooler weather. It is evenly distributed on both sides of the transom and runs up onto the back edge of the swim platform, does not seem to be worse on one side than the other. Does the ECM's need to be recalibrated? What else to look for? I hate cleaning the mess up after every run. Boat seems to be running very well.

What gas are you running? I think if you run anything higher than 87 octane, you get a lot more soot.

Run your engine serial numbers and ECM part numbers by your local MerCruiser rep. and see if there's a fix campaign or recall on your stuff. I'm sure you're not the first guy to have this problem and if ANYBODY knows what the fix is...MerCruiser does. Good Luck.

Gerrit,
I have the same boat as you, and I get about 1/10 the amount of transom soot with my 525's that I got with my 2004 Baja 33 Outlaw with 496 Mag HO's. That boat had a terrible soot problem, but the engines always started and ran flawlessly. I only use 87 octane, I add Star Brite enzyme water removal because of the E10 gasohol, and the 525's run flawlessly also. With very little soot.

O2 sensor???

Running a long time on the Rev limiters will create the Black soot, but if that is the case there is nothing you can do.

Early 525EFI's needed to be reprogramed by Mercury to eliminate the Soot you would get from not running on the Rev-Limiters.

I don't run on the rev limiters all of the time:eek: just some of the time. I run 87 octane marine fuel. I am leaning towards needing the ecm's reprogrammed.

I had to have mine reprogrammed. It was running very rich at idle. I still get a little bit of soot from idling, but nothing like before. Call the tech guy at Merc with your engines' numbers. He should be able to look it up quickly to see if it needs to be reprogrammed.

Try a hotter plug too.

Now what takes the soot of the transom? I have tried many products but take it all off?

I have had excellent results with Spectro XL-1 motorcycle wash. It also works well on removing brake dust from aluminum wheels.
Ken

When we wash our boats it goes directly into our brackish lake, so I use Simple Green. It is biodegradeable and it seems to work fairly well. It does work well on the rest of the boat. Need to do a little scrubbing, but I can still see a slight stain on the back edge of the swim platform. I will probably have to buff it out with a lite compund type cleaner/polish.

You would be supprised how well Method wipes work.
(I pick them up at office depot- believe it or not)
I tried them one day when I was in the shop goofing off.
My wife threw them out, so I dug them out of the trash can and figured I could use them for something in the shop.
Can't believe how good it works.

Running too rich and you have black soot on the transom.

Run too lean and you burn holes in your pistons.

The former is better than the later.

Lean out the carb just a smidgeon.

# 50 cleaner wax will get the soot off.

Try 3-M Black Streak Remover or Mequiar's Black Streak Remover. Spray on and wipe; will take it right off:D

Use the 3M - I'm a shareholder:cool-smiley-011:

The Works tub and tile cleaner. You can get it at the Dollar Stores.

I have used West Marine hull cleaner which is some strong stuff it seems to take some off but not all. Is it possible for the soot to stain and never be removed?

525 soot
 

Just joined the forum,have been reading for a while and finally joined so I can play while working.I have 525s in my Hallet 300 and the starbord motor soots the transom as well as dirties the oil more than port but the port motor does not.I have only run 91 octane in it and thought that was the problem but they are not both doing it.Sounds like I may have a bad O2 sensor also,both run great with no problems.Any input??I only use Amsoil Dominator oil in these.