Black Soot Normal **PICS**

[b1gdog83]

I have a 2017 200hp with 100 hours. I’ve noticed black soot on the outside of the lower unit. Is this normal?

[Zuki175]

Does your lower unit exhaust at the prop bubble like a jacuzzi when submerged? Just curious, but that does not look normal.

[b1gdog83]

Where is the lower unit exhaust?

[Zuki175]

Lower unit exhaust exits from the propeller and also a port hole above the waterline below the cowling release handle facing to the rear.


How many oil changes have you had since new?

[b1gdog83]

I have done the 20 hours service oil change and just hit the 100 hours so plan on doing another one shortly. Anyone know what could be causing the black soot?

[Solarman]

When idling, exhaust gases exit non-sealed areas above the prop (most often less backpressure, closer to surface). Many areas above prop are not sealed, to allow drainage, and filling of lower unit areas for water to saturate exhaust and pump chambers. Most exhaust exits through prop when in forward, as this pulls exhaust (motion of prop and boat moving forward), but reverse puts extra water pressure on prop against exhaust, same as in neutral idling, so some exhaust exits those areas where water enters. It is not uncommon to have those carbon deposits, just like inside the prop, in those areas that gases exit.

Good luck. Enjoy your boating.

[b1gdog83]

That actually might explain it Solarman. I have been doing a bunch of deep dropping lately and have been leaving my engine just idiling while dropping. I also have been keeping it in reverse while dropping to negate the current.

[b1gdog83]

Ive also have been told the cause could be from bad fuel or a bad seal in the lower unit. Anyone have thoughts on those possible causes?

[Greg Moore]

Bad fuel? No, bad seal in the lower unit? No.. Where that is coming out there is no seal, just metal to metal and not that well machined either. Stick your finger in your car or trucks tail pipe, black right!? And that's after going through a cat, no cats on your outboard and they tend to run a bit richer than a modern car so even more soot. Drive it! Clean the black off if it bothers you but unless you see oil running out there, you have no issues.. Next time buy it black paint

[redlowrey]

Something does not add up here, in this post you are talking about black soot staining the engine cover, in an other post you are asking about a 3.2 code with a map sensor problem.
When does the check engine light come on, when you are cranking the engine or when it is running, If you have got a problem with high signal voltage on the map sensor you will definitely see soot on the covers.
Pull a plug out of a cylinder and look at the porcelain centre of the plug, and come back on the forum telling me what colour it was, black, light tan, or white,

[b1gdog83]

Something does not add up here, in this post you are talking about black soot staining the engine cover, in an other post you are asking about a 3.2 code with a map sensor problem.
When does the check engine light come on, when you are cranking the engine or when it is running, If you have got a problem with high signal voltage on the map sensor you will definitely see soot on the covers.
Pull a plug out of a cylinder and look at the porcelain centre of the plug, and come back on the forum telling me what colour it was, black, light tan, or white,

The 3-2 code came on when I was starting the engine. It wouldn't crank over and stalled out for a couple minutes while I was receiving the 3-2. However then it started and I ran it for another 2 hours and never received the code again. I've been told by my mechanic if the 3-2 code only went off once there was no need to bring it in to get it looked at. I was told to keep running it and see if I have the code go off again. However when I pair the 3-2 code with the black soot I just want to make sure I don't have a serious problem.

[redlowrey]

That is why I want you to pull a plug out and tell me what the colour of the porcelain is, it would be no good telling you to check the map sensor you wouldn't know how. The map sensor is the most important sensor on your engine, it tells the ecu how much fuel needs to be injected into the engine. It makes sense to me now why your 3.2 code came on, that code was lodged because the ecu did not see a change in the signal voltage on the map sensor when the engine was cranking.
The sensor works like this, it has a five volt supply a ground and a signal voltage, when the key is on the ecu will see a bit over four volts on the signal line, when you crank the engine over it produces manifold vacuum in the inlet manifold, this inturn will change the voltage on the signal line and the ecu see's this change and injects the correct amount of starting fuel, correct amount of iac bypassed air along with manifold air temp, engine temp, and when your engine was not cranking good would have brought the light on.
There could be something brewing in the system who knows lets start with the colour if a plug.

[b1gdog83]

Redlowrey I will pull the plug tomorrow and post a picture of the color. Do you know the spark plug socket size by any chance?

[Harper]

Redlowrey I will pull the plug tomorrow and post a picture of the color. Do you know the spark plug socket size by any chance?

5/8"......

[b1gdog83]

Here are some pictures of the spark plugs.