Black film by exhaust ports

[bfrank]

Is my engine running to rich if I get allot of black stuff on the back of the boat by the exhaust ports????

[96PRE2000WT]

I have the exact same thing going on and was wondering the about it as well.

[neilm]

Probably not. One of the consequences of having your exhaust 'water cooled' on the way out is that the soot doesn't get dispersed into the atmosphere the same way as it does on a car -- it sticks to the hull for you to clean, instead.

[bfrank]

So then that is normal??? My old boat didnt seem to do this and it was the same motor.

[jeffro]

i had an I/O that was getting build up on the transom...the tech said it was running a little rich so they adjusted it. seemed to cut way back on the buildup.

but i'm no tech, so i'll leave it to the mechanics for a verified answer.

[tobo57]

black grime

I've always had a that grime on the back of my boats.Now with my first new boat I'm waiting to see if it is still a problem.

[Domsz06]

well i'm no tech, but I have worked on cars forever. here's my .02 all cars emit emisions, so do boats. and like neilm said since we are all water cooled then the exhaust can't compltely disperse it sticks to the boat. All engines are set to be a bit rich. Rich=less problems. You run an engine lean, and your asking for problems. Since the exhaust is in the water, you can't get it out. Kinda like when you drive your car in the rain, if you have an under car exhaust(sport cars dumping their exhaust, or trucks too) you will notice that your car is a bit blacker in ther rear. I would venture to say that that's the same thing as the boat, so therefore you really don't have a problem. Now, if you have enough exhaust to see the black when you driving, then that would be a bit too rich.

Another thing to consider is when you drive your boat, you are normally pulling people correct? well, I know when I drive i tend to bump the gas a bit, and then slow down, well the bumping will dump more gas in the engine, and it might not burn all the way, so then you have the excess being blown out the exhaust, and there's your black stuff again.

*stepping off my soap box*

Dom

[neilm]

Originally posted by bfrank
So then that is normal??? My old boat didnt seem to do this and it was the same motor.

What I was stating was that some soot is normal. Since you're stating it's way more than your old boat, then get your dealer to check out your engine. I kinda doubt it, though, the EFI set-ups are fairly accurate these days.

There are many variables to consider.. Don't forget that a cold engine runs rich until it warms up. Are you currently running your new boat in colder temps than your old one?

Good Luck

[blr]

doubt that your running rich with an ecm controlled engine. the ecm will correct the air fuel micture based on either egt or o2 sensors. it is also quite likely that there is no adjustment other than reporgraming the ecm. typically if you adjust the air intake in anyway, the ecm will automatically adjust the fuel rate to compensate. this is the same reason you no longer have to make adjustments when you change altitudes with your boat. in older non-ecm controlled engines, you would have to adjust air/fuel mostures as well as timing to adjust for large (1000') or more altitude changes. not any more. jst my .02

[pup]

check out the air intake, make sure the filter/flame arrestor is clean. is the engine coolant coming up to operating temp? coolant should run at least 160. is the engine using oil? maybe the residue is not fuel.

[bfrank]

What is the max temp it should run, mine will get just over 180 before the thermostat opens. It always seems to run around 180 degrees.

[Tige M.D.]

Most marine efi egines are set to run fat (rich). A lean condition in the hands of the typical boater will melt down in a weekend.
There are no egt or 02 sensors on Merc or PCM. They are an open loop system(load, speed, density).
If it is a Merc check with your local Merc dealer. The 8.1 liter was doing this and they had reprogrammed the ecm to lean out at idle. As far as I know if it is under a year they cover it under warranty.
Also, a bad engine coolant temp sensor (ect) will cause a rich condition. This can be checked with a scan tool.

[Tige M.D.]

180 deg. is perfectly normal. Any hotter than 200deg and you are loosing an impeller. Big trouble.

[bfrank]

My engine is not fuel injected, will that make a diffrence???

[Tige M.D.]

Sounds like a carb adjustment is needed. Try leaning out the mixture screws 1/8 turn each. Do a little at a time and be patient.