Sailing Yachts
Sailing yachts present special problems as another factor enters the equation, that of heel. Yacht exhausts are often offset from the centreline, and while the outlet may be well above the water normally, it can be well below it when the yacht is heeled over.

Overcoming the heeling problem is a question of making sure that water can't run down towards the engine in normal circumstances. The designer must ensure that the top of the swan-neck is always well above the waterline, even when the boat is heeled to its maximum. Obviously, nothing other than a closed gate valve or seacock at the hull skin fitting can protect an engine if the exhaust system goes completely underwater -as in a knockdown or capsize -and many yachtsmen choose to close the gate valve as an additional precaution once the engine is switched off. Of course, one must remember to open it again.
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Exhaust Configurations