Pretty good article from Steve d'Antonio. In summary, both are good and both can be well designed and trouble-free. He likens it to anchor
yachts are almost always delivered with dry-stack exhaust. I know a guy having his second one built - this one with wet exhaust. He cites factors of soot and accessibility to maintenance
items, meaning you can easily change an impellor from inside the boat, but need a diver to change a zinc for a keel cooler (also cited in the Steve d article above). Both boats were multi-million dollar boats, and I am sure he will take a small price
hit when time comes to sell his wet exhaust Nordhavn as they are synonymous with dry stack, but tough to argue with a guy who has owned two and decided second one would be wet.
I also know a guy who had a Willard
yacht built. At the time, he was a VP with Willard
and specified his engine to be wet exhaust but with a keel cooler instead of the traditional heat exchanger
. At the time, seemed like a great idea, but I wonder where one would fetch broken impeller vanes if needed as they always land in the heat exchanger.
Finally, I know of a Chinese builder
of George Buehler designed Diesel
Duck trawler yachts in steel. Knowing that dry exhaust have marketing
appeal with the offshore
trawler set (e.g. Nordhavn), they delivered the early ones with dry stack. They had problems with overheating
due to inability to evacuate massive amounts of heat given the configuration limitations of running the stack through living quarters. Turns out that most recreational dry stack boats have huge, expensive blowers that are as critical to cooling dry stacks as raw water
pumps are to wet exhaust. The Chinese builder
quickly turned to wet exhaust and will no longer construct with dry.
In the end, no free lunch. For recreational boats, I'm almost positive a dry stack is much, much more expensive than a wet exhaust. Probably by several multiples.