Exhaust flappers

[Arnold]

I heard people having exhaust flappers to avoid water to enter the engines when stopping the boat.
Would you need them also if the exhausts are on the side? Thanks

 

[Robski97]

I dont believe that's the reasoning behind the flaps. Mine have been missing since 2006. Both motors and genset had them and they exhaust out the sides.

Rob

 

[CurrentSea]

The flappers on the back of the boat are because when a boat slows down water rushes in and could rush up risers if a motor suddenly stalled.

There are also flappers inside the risers sometimes but these typically don't last very long as they usually burn up after one bad impeller episode and is not noticed until the riser is removed!

I don't think there is as much risk on the side of the boat as the back.

 

[Sandy]

They also help to reduce exhaust noise levels at low rpms.

 

[JohnC]

You don't generally see the flappers on side exhausts. My boat actually has side and transom exhausts and the transom ones have flappers and the side ones (which are the larger primary exhausts) don't.

 

[Sandy]

Although relatively uncommon, I believe at least some side exhausts have recessed flaps , similar in concept to sterndrive exhaust flappers but close to the hull outlet. Exterior flaps, as common on transom outlets, when placed on side outlets may be more vulnerable to wave action for shorter life.