Wet exhaust tail pipe flappers…pros and cons?

[lwarden]

Perhaps some, but the unique circumstances for water to back up an exhaust pipe are still present in a 45* corner outlet. I believe the two main reasons for that configuration are noise and soot. It is more difficult (expensive) to do it that way, easier to come straight out a transom.

Much exhaust noise heard on a vessel is reflective noise off the wake. By exiting at 45* this reflective noise is reduced.

And the "station wagon" effect is reduced by the 45* exit as well. By exiting into the air coming of the side of the boat exhaust is carried more aft and not into the low pressure area immediately behind the broad, flat transom when underway. This keeps the transom cleaner and exhaust odors are reduced.

Our exhaust is out the side at 45 degrees and I can attest to the lack of soot on the transom. Hard to tell about the sound since I don't have a way to compare it on this boat, but it makes sense it would be better to blow the noise maker out at that angle vs, straight back.

 

[Southern Boater]

Perhaps some, but the unique circumstances for water to back up an exhaust pipe are still present in a 45* corner outlet. I believe the two main reasons for that configuration are noise and soot. It is more difficult (expensive) to do it that way, easier to come straight out a transom.

Much exhaust noise heard on a vessel is reflective noise off the wake. By exiting at 45* this reflective noise is reduced.

And the "station wagon" effect is reduced by the 45* exit as well. By exiting into the air coming of the side of the boat exhaust is carried more aft and not into the low pressure area immediately behind the broad, flat transom when underway. This keeps the transom cleaner and exhaust odors are reduced.

Some good points there KD, the station wagon effect is also an issue, we keep all aft facing windows and doors closed during passages for this reason.

 

[Brooksie]

Here is a drawing offered by Tony Athens of the minimum dimensions for a safe exhaust system. When the "point" referenced in the drawing is several inches below the spill over point then the water will run back out the exhaust and not get into the engine.

David

If the water-lift should fill from wakes or hobby-horsing while anchoring in a seaway; then, water would next spill into the engine as if the water-lift were not there.
IMO, the water-lift muffler allows you to use a gooseneck inside the transom or just raise the outlet higher on the transom but by itself is not a cure for the above problems.

 

[Keysdisease]

If the water-lift should fill from wakes or hobby-horsing while anchoring in a seaway; then, water would next spill into the engine as if the water-lift were not there.
IMO, the water-lift muffler allows you to use a gooseneck inside the transom or just raise the outlet higher on the transom but by itself is not a cure for the above problems.

I have seen goosenecks comin off lift mufflers going into cockpit cabinetry to get good height, higher the better staying inside backpressure specs