Exhaust Flappers--which way to mount

[CraigO]

I have 1989 Bayliner 24' Cruiser with 5.7 liter sterndrive. The thru hull exhaust (above water line) is equipped with rubber flappers on the exhaust. Which way should they open? Should the open end be down (ie opens upward) or the open end be on the top side (ie opens downward)? or possibly even sideways. The reason I ask is I see in boating mags that they seem to be mounted with the opening on the bottom (opens upward--swings upward), but my mechanic insists they open downward (swing downward with opening on top). Which is right?<br /><br />Also on another note: My boat was equipped with dual exhaust on the transom,but the headers on the engine merge in to one exhaust tube on the starboard side and exit out the starboard exhuast fitting only. The transom fitting on the port side "must be for show only" as there is nothing connected to it. Is this ok? My mechanic says it is not has it will cause uneven backpressure problems from the engine. Is he right? Is this that big of a deal? I would hate to have to redo the whole exhaust system

 

[johnkc]

Re: Exhaust Flappers--which way to mount

craigo,the hinge of the flapper is at the top ,thus the opening is at the bottom. if the exhaust was a factory installation i would leave it alone.

 

[BigBabyLou]

Re: Exhaust Flappers--which way to mount

John's right. The flapper is hanging off the hinge and it opens with the flow of the exhaust gas. Make sure it closes well with pressure from the other side.<br /><br />Lou

 

[Bondo]

Re: Exhaust Flappers--which way to mount

I think you need a New Mechanic.....

 

[Trent]

Re: Exhaust Flappers--which way to mount

Ditto what Bondo said!!

 

[taz33911]

Re: Exhaust Flappers--which way to mount

If you turn it over the flapper would stay open all the time letting water surge back in when you slow down and guess what it ends up in your cylinders not a good thing best bet leave it alone.There is a counter weight on the flapper it only works one way .

 

[Walt T]

Re: Exhaust Flappers--which way to mount

Yea, he needs a new mechanic allrighty. Hinge is up. As for the Y in the exhaust, that actually helps. A little backpressure is good and will help scavenge the cylinders. This is why you see small 'venturies' in exhaust systems of professional racers. Ever see the little tube connecting dual exhaust systems together under a car? That is so both sides of the engine benefit from the exhaust pulses generated and will help scavenge the cylinders. Still, with the large diameter exhaust system on boats, I really doubt there is much backpressure on your system. If you want to change it to both sides, I really dont think it will make any difference performance wise.

 

[golfer]

Re: Exhaust Flappers--which way to mount

Your mechanic is out of his mind...Flap opens from the bottom, hinge on top...Does his breath smell of alcohol?