With 16,000 miles now on Wind Horse we’ve zeroed in on a couple of things that we want to fine tune. One of these is the level of engine noise and/or vibration. Mind you, at our cruising speed of 1900 RPM/11.3 knots this is just 57 dB in the saloon/bridge area, so the noise level is already very low. But when you are passaging for thousands of miles, what would be considered almost silent on most boats can become bothersome.

As we are in Ventura, California, we called our old friends Dale and Steve who own and run Ventura Harbor Boat Yard. Steve came down with his yard foreman, Tom, and they gave the exhaust system a quick look.

Tom immediately noticed that there was a slight low spot in the port exhaust run. The low spot could allow cooling water to be trapped, which would then be periodically blown out the end of the exhaust line. The on-again off-again nature of this water being blown out can be noisy, disturbing the otherwise steady drone of the engines. So, we rerouted one fuel line, adjusted a couple of exhaust hangers, and made the exhaust run straight downhill as it should have done in the first place.

Steve James suggested we go for a short sea trial, out to the Ventura Harbor sea buoy and back, so he and Tom could listen to the engine and check for vibration.

We were pleasantly surprised to find that part of the noise that had been bothering us was now gone – the result of a ten-minute straightening job on the port engine exhaust.

Tom checked the structure surrounding the engine and the exhaust hanger plates and found no vibration, except at idle – which confirmed what we had felt.

Steve James (left) and Tom are checking the specifications on one of our spare flexible engine-to-exhaust couplings.

These flex couplings allow up to an inch (25mm) of movement and rotate on their flanges as well. Actual engine movement is about 1/4″ (6mm) at lower speeds.

The actual machinery noises emanating from the engine room are pretty low. Steve James had us open all three of the doors between the saloon/bridge area and the engine room, and then close one after the other, noting changes in engine noise as this went on. We then opened the watertight door from the saloon to the aft deck and again checked what we were hearing.

This simple experiment confirmed what our own ears have been telling us, that it is exhaust noise rather than machinery noise which is the problem.

Wind Horse has a straight through wet exhaust, with a check valve in line, but no mufflers. We originally left mufflers out of the system as it is slightly more efficient, and we were hoping that with the low power requirements of this boat, mufflers would not be required. Steve James suggested we look at installing mufflers to reduce the exhaust noise. However, after checking with various companies – including looking at a very interesting underwater exhaust – we decided that the impact on engine room space was too great. One of those many tradeoffs in boats. Want it quiet with lots of space in the engine room, or super quiet with a lot less space? We opted for more space.

The two Steves – Dashew and James – were looking at the exhaust system one last time, prior to launching last week – and Steve James said “what if we tried a 90-degree elbow off the transom? This might just change things enough to do what you need.”

The yard ordered a pair of these 5″ (15mm) rubber elbows and clamped them on.

Here is a close up. Note the double hose clamps. We’ll need to trim the excess thread so it doesn’t damage our visitors’ inflatable dinghies.

And the result. A small miracle! The resonant exhaust noise that previously was an annoyance is now totally gone. At our 1900 RPM cruise (11.3 knots) speed, the ambiance in the saloon and bridge area has improved dramatically – and it was already very nice before.

The irony here is that we had looked at changes to the exhaust system costing upwards of $15,000. This approach? A pair of $65 elbows and four hose clamps.

All of which proves once again that trying the simplest approach often yields the best results.