exhaust valve

[superboots]

I shall be replacing my rubber exhaust pipe. Should I use this opportunity to fit a ball valve - perhaps at the top of the gooseneck - as an extra line of defense to prevent the engine being flooded? Are there any disadvantages in doing this. The pipe is 60 mm diameter so the valve will be very big and heavy and expensive!

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[Stuart_Wyatt]

My old boat has a different solution to the ball valve, more low-tech. It has always had a gate valve skin fitting at the exhaust exit, to be closed when sailing off across the blue stuff, or during winter.

If your present swan-neck does the job, and you've no reason to think the exhaust system will flood, why bother changing anything? You might increase the back pressure in the exhaust system, which (with a diesel) would reduce performance and could cause other problems.

Health warning: this advice comes from not an engineer!

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[johnsomerhausen]

I;ve got an even lower-tech solution on my boat. Put a flap over the exhaust through-hull fitting so that the gases can exit easily but if a sea pushes against the rubber flap, it closes it. Those can be bought ready made here in the US but you could easily have the plastic ring turned on a lathe. The rubber only lasts two or three seasons, but it's easy to make copies yourself.
john

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