diesel smoke on stern

[Donna12924]

Hi thereWe have a problem on our C27 with diesal smoke film on the transom. The exhaust goes through a thru hull, there is no provision for flap on it. Any suggestions for how to handle this problem, or do we had to retrofit with some type of thru hull with flapper?? What have other owners done? We cannot be the only boat with this problem. Thanks much

 

[Ray Bowles]

How much load is the engine under?

Diesel motors will produce heavy dark smoke if run under to heavy of a load or if run at too high of an RPM. A fouled prop or wrong size or pitch on the propeller can also load the engine. Usually running just 50 to 200 rpm less can produce a large film improvement with little loss in boat speed. These are cheap ideas to try. 100rpm lower on our 38 foot boat, with a 44hp Yanmar, made the "soot" disappear. Flappers help keep following seas and waves from pounding up the old stink pipe when the engine is off, but offer no "de-sooting" help while running.Hope this helps, Ray.

 

[ken]

smoke

Another cause of smoke is bacteria in the fuel. Might want to try some biocide.

 

[Big Windy]

Smoke

I have been told a bit of smoke is perfectly normal...just like auto exhaust smoke...I just wash mine off after sailing. Takes some diluted Simple Green and a long handled brush, comes right off.

 

[Bill]

Ray is right

Black smoke indicates not a complete burn of all the fuel being supplied. Over acceleration can cause this, the same way a truck smokes when starting to accelerate. Not allowing the engine to warm up enough before starting out can cause it. Worn rings can cause it. Marginal fuel is a possibility. If it is excessive and constant a mechanic may be needed to run some tests.

 

[Randy6414]

Exhaust on transom

The C27 tends to squat when running under engine power, and this leaves the exhaust through-hull under water. Exhaust bubbles up and sticks to the transom, leaving a sticky gray film.I apply a couple of good coats of wax to the transom in the spring, when I do the rest of the boat. This makes it easier to wash the film off the transom during the season.Clean fuel, clean injectors, and not overloading the prop are all important. Backing off the throttle a bit helps, too. Running full bore increases squatting, increases exhaust smoke, and adds to the transom film. Still, I find that even with everything in good condition, it's necessary to wash the transom with a brush and soapy water after each run, or I wind up with a build-up.Randy