We get soot on the transom and in the cockpit areas over time. Was looking into mechanical issues and tune up but decided that's probably not the issue. Engines (8-92TI's) start with no smoke and run super clean. Zero visible exhaust on plane. Clean air filters, intercoolers, and good turbo's.

But we still get the soot buildup on the paint. If we go into a strong headwind it builds up quicker. Calm days or wind behind us much less. Also we get salt mist spray in the same areas more in head wind and less in tailwind.

So basically seems like a big station wagon effect compounded by the under gunnel air intake. Not sure if the amount of air drawn into ER is enough to be a factor. Also we have a full 4 sided enclosure with no openings ion the back other than ladder area.

Wondering if others experience the same. Most SF's have the ER vents on the side. Guessing responses will be limited.