Smoking exhaust,

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hfmckevitt

Veteran Member
Joined
Oct 24, 2015
Messages
68
Location
USA
Vessel Name
Linda Lee
Vessel Make
45' Aquarius motoryacht
We have twin 3208T, cat engines. This maybe normal, but being new to these engines, I must ask.
As we travel the back of our boat gets covered gray from our exhaust.
Is it normal or do I have an issue with the engines.

Henry
Linda Lee
 
How long is travel time? Does the engines reach WOT rpms? I have also found for me buying Valvtec (sp?) fuel greatly reduces the residue on the back of the boat. Also depends on wind direction the amount of station wagon effect.
 
Normal if you idle then power up and down a few times a day. The longer the idle periods the worse it usually is.


The solution is for many is don't wax your transom and if you put anything on it one of the very slick polishes is recommended. I cant recommend on but some here sure can.
 
Is the complaint smoke out the taipipes or soot on the transom? Not clear from OP's post.
 
If the exhaust is almost clear or clear after warmup, then it's normal. A little white smoke is steam from the exhaust water. Since the exhaust water is the water you're running in, the dirtier the water, the more debris you exhaust to foul the transom.
If you are getting exhaust smoke, you might post the color.
Some engines can have have exhaust nozzles fitted that release the exhaust underwater. The military uses them for covert ops.
 
3208s are known to smoke a LOT after powering up aft a prolonged idle.....it is probably just soot that is darkening your hull.
 
Soot on tramsom

The exhaust is clear, the soot is gray. We have been traveling from Ft Myers Fl, up the ICW to NJ.

Using different feel types along the way.

Thanks
Henry
Linda Lee
 
Years ago used them in some Ag. tractors. Black smoke was usually a sign of a dirty air filter, from dusty field work. Normally that's not a problem on a boat but maybe check your air cleaner filter to be sure it is clean and in good shape.
It could be other things but this is an easy one to check first.
 
Last edited:
Before declaring it normal several things need to be considered.


Is it from both engines?
Do you reach top rated RPM?
What is boat size and how fast are you running? What RPM?
 
OP is asking if grey exhaust film on the transom is anything to worry about. Grey sounds like a thin film of exhaust soot and IMHO is normal.
 

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