One of the very few disadvantages of the dry stack that is found on most Nordhavn Trawlers is that they will occasionally blow soot all over the back of the boat (or worse, your neighbors boat) when starting up a cold main engine. Over the past six months of use, we have discovered that this primarily occurred after heavy rainfall had washed built up soot down the stack to blown back out on start-up.The trick to avoiding the soot in the first place is putting a rain cap in place while the boat is parked (you will see the commercial fishing boats using a bucket for this). Scroll down past the end of the article to see Scott’s version of a rain cap made from 5″ PVC. One additional way to help prevent the accumulation of soot in the first place is to run the engine exhaust hot enough to burn the soot periodically, which means running the boat at near full throttle until you see the exhaust smoke clear (~ 10 minutes).
The above will help with soot, but not completely prevent it. That is where the Soot Sock comes into play. When starting up the boat in a marina with calm winds, we usually cover the end of the exhaust with a Soot Sock to catch any of the carbon particles exiting the stack on start up. We have two versions of the sock and use both, depending on the wind direction.
Our original Soot Sock is a simple black plastic flower pot (the flexible, disposable ones from a nursery) with a black ladies nylon stocking taped to it. A 1″ PVC elbow is bolted to the pot to allow the Soot Sock to be deployed and recovered with a boat hook. This sock works well if the wind is coming from the bow and you are very careful when removing the Soot Sock so that it doesn’t tip forward and drop soot all over the boat deck.
In less favorable wind conditions, we use version two of the Soot Sock. It is made from an 8″ long section of 5″ PVC pipe, cemented to a 45° elbow. A black, ladies nylon stocking is attached to the end of the elbow to catch the soot (with a hose clamp). There is also a short section of 2″ PVC bolted to the side that allows deploying/recovering the sock with a boat hook.
While much heavier than our flower pot design, the 5″ PVC Soot Sock catches and holds soot very well since the bend of the elbow creates a natural catchment for the soot to accumulate in that does not blow all over the boat when recovering the soot sock.