can i remove these flappers?

[t0mmy91]

Hi! going more in depth of my searay project boat. i purchased a conversion kit to go from a one piece manifold thats no longer made, to the 2 piece manifolds. i have heard opposing opinions on these exhaust flappers. can i get rid of them? they dont look like they would even do anything. should i replace them or leave them out?

 

[Lazy Daze]

"Those" don't look they would do anything. It appears the rubber parts have either fallen off or melted off due an overheat situation. The rubber parts have fallen further down the exhaust tube.

Flappers are there to (hopefully) prevent your engine from ingesting water from a large wave hitting your stern (whether from another boat or induced by coming off plane too fast).

 

[Skybolt]

Regardless of there function, I always removed them. An outdrive boat isn't going to see the water rush that a straight engine boat would see. I found that they would eventually deteriorate to the point they would fall off and clog the exhaust.

 

[t0mmy91]

"Those" don't look they would do anything. It appears the rubber parts have either fallen off or melted off due an overheat situation. The rubber parts have fallen further down the exhaust tube.

Flappers are there to (hopefully) prevent your engine from ingesting water from a large wave hitting your stern (whether from another boat or induced by coming off plane too fast).

yea i agree, but i remember reading something somewhere that mercruiser said if they are there and functioning leave them, but if they deteriorate, dont replace. anyone else hear or read anything similar?

 

[Lazy Daze]

yea i agree, but i remember reading something somewhere that mercruiser said if they are there and functioning leave them, but if they deteriorate, dont replace. anyone else hear or read anything similar?

I don't recall ever reading something published by Mercruiser that said that.

I see what Orlando said and I think, for the most part, he's right... the chances are low. But I can also tell you that about 3 or 4 years ago we had a boat come into the shop with a stall/no start issue. After discussion and investigation this exact scenario I mentioned turned out to be the cause.

 

[t0mmy91]

I don't recall ever reading something published by Mercruiser that said that.

I see what Orlando said and I think, for the most part, he's right... the chances are low. But I can also tell you that about 3 or 4 years ago we had a boat come into the shop with a stall/no start issue. After discussion and investigation this exact scenario I mentioned turned out to be the cause.

ok gotcha. i just dont see how they work. are they supposed to be flat out across the exhaust most of the time and just flap when exhaust is exiting? looks like mine are just hanging there, and wouldnt seal anything, guessing mine arent supposed to hang down in the exhaust like that?

 

[Skybolt]

ok gotcha. i just dont see how they work. are they supposed to be flat out across the exhaust most of the time and just flap when exhaust is exiting? looks like mine are just hanging there, and wouldnt seal anything, guessing mine arent supposed to hang down in the exhaust like that?

The problem is they were spring loaded closed and opened when the exhaust pressure was present. After a few weeks of hot exhaust temp they stayed flopped open. Great idea, bad implementation.

 

[t0mmy91]

sounds good, ill just grab a new set from amazon. they have quicksilver set for $83

 

[keokie]

The problem is they were spring loaded closed and opened when the exhaust pressure was present. After a few weeks of hot exhaust temp they stayed flopped open. Great idea, bad implementation.

Admittedly, they are not a great design, but they do tend to separate and close the tube when a rush of water flows agains them.