I used to sail on steam powered containerships. The "station wagon effect" at high speeds would produce black "sootdrifts" on the aft deck that were several inches deep where the wind deposited it. Kind of funny (not for the owner) but we once had a Taiwan trawler yacht as deck cargo from Kaoshiung to Seattle and after a week of high speed running and strong winds the tarps covering the thing were in shreds and every part of it was covered with a layer of ultrafine soot an inch deep inside and out. Somebody is probably still trying to figure out why he keeps finding soot in the strangest places. Back on topic though ... dry stack generator exhausts are prone to problems of all sorts. As everyone knows, generator exhaust is nearly always cool, too cool for the most part. For every pound of fuel burned in the engine, nearly a pound of water is produced. In a long run up a dry stack the water vapor in the exhaust will condense and coat the pipe walls. That makes a wonderful surface for soot to collect until it reaches the point where gas flow or vibration causes a sheet of it to break off and land on Mrs. Owner's suntan oiled belly. This is not part of the yacht life she expected and some poor engineer is in for an earful. I am glad you added external cleaning and filtering. Even a Tier IV 500kW generator will discharge more than 1/2 a pound (240gm) of particulates each day and much of that is going to collect in the piping long enough to make an impression the Mrs. won't soon forget. If drystacks really were, life would be much better but they are not dry, they don't get hot enough and stay hot long enough to stop acting like little hydrocarbon condensers where carbon, hydrated hydrocarbons, sulphates, and vapor phase aromatics have a reunion before leaving for more sunny locations or sharing Mrs. Owner's beach towel.