Question: I have a pair of Detroit Diesel 6-71 TIBs in my 1990 Ocean 48 Super Sport. I love both the boat and the motors, but the Detroits have always been loud at the exhaust end of things. As I grow older, this noise is starting to bother me, particularly at times when I have to shout to be heard on the flying bridge at cruise speed. Muffler companies tell me that modern muffler technology’s not much different than it was back in 1990. So, believe it or not, I’m thinking about adding a swim platform to dampen the racket. Suggestions? —Ian B. Bass, Purchase, New York
Professor Diesel: Noisy exhaust from diesel engines in a marine application is a common concern. Everyone wants his boat to be as quiet as his car. Unfortunately though, this isn’t going to happen. While a whole lot of noise-reduction research has been done over the years, I’m afraid the folks you’ve talked with at the muffler companies are right. Things haven’t changed much.
Upgrading or changing an exhaust system, by the way, is very expensive. I have friends who have had it done on their boats. Some have been happy with the results and others have noticed little or no difference. I always suggest that before anyone makes a significant change on his boat, he should examine another boat or two that have been similarly altered. At minimum, he should at least talk to the boat owner who’s living with the change. And also remember that what works on one hull may not work on yours.
Adding a swim platform? Properly installed swim platforms do seem to make some difference. But again, before going to all that expense, try to hitch a ride on a boat that’s like yours (but with a platform) to check out the noise levels.
One final point. It is a very good idea to change your seawater-pump impellers at least once a season. Even a small reduction in seawater flow can make a huge difference in exhaust noise. Making sure your seacocks are fully open and your through-hulls are totally clean may also help.
Professor Diesel is Larry Berlin, director of Mack Boring’s Training Services division.
This article originally appeared in the November 2010 issue of Power & Motoryacht magazine.