Exhaust Flappers

[Striper Blues]

Anyone out there know anything about the exhaust flapper(s) used in a 3.0L OMC Cobra?<br /><br />I'm told there are "rubber" flappers. I only see one metal flapper right at the top of the exhaust pipe, but nothing anywhere on the boat or in the manufactures part catalog.<br /><br />Is it common to add some "custom" flapper dealie?<br /><br />Anyone familiar with this?

 

[Boatin Bob]

Re: Exhaust Flappers

Go to this link and you will see your flapper, it's item # 81 and that's all there OMC 3.0 ltr cooling is

 

[Striper Blues]

Re: Exhaust Flappers

Thanks Bob, I did see number 81 the seal as they call it, but my mechanic is talking about some type of separate rubber flappers. I don't see them anywhere in the parts catalog. <br /><br />I'm guessing its some aftermarket add on? He is concerned about back pressure when slowing etc.

 

[elpaso]

Re: Exhaust Flappers

# 81 - Exhaust seal- as they call it- is a flapper. It prevents water from backing up your exhaust and going into engine.

 

[Striper Blues]

Re: Exhaust Flappers

Is the metal supposed to have a rubber coating of some sort? Mine is just a metal flapper<br /><br />thanks....

 

[MrBill]

Re: Exhaust Flappers

Your mechanic is using Merc terminology and seems to be familiar with the Mercruiser type flapper, which is rubber with a stainles steel flat pin all the way through to position it in the holes of the cast aluminum exhaust.

 

[Striper Blues]

Re: Exhaust Flappers

Has anyone heard of mechanics using the rubber merc flappers in place of the metal OMC flapper at the top of the exhaust pipe on a 3.0L??<br /><br />What would the advantage be, do they operate more reliably?

 

[MrBill]

Re: Exhaust Flappers

The Mercruiser flapper is a different configuration. It is two "flaps" suspended in the middle with a stainless pin that is held in the exhaust with two square grommets. Based on the OMC diagram, the exhaust contact points are in a different position and will not accept the Merc part. Additionally, the diameter is probably a different size...all in all...you'll need to get the OMC part for a proper fit.

 

[VMAX]

Re: Exhaust Flappers

This is troubling me now.<br />I discovered a water leak into my bilge coming from a small hole in the exhaust pipe, so I plugged it , thinking that it might have been a hole caused by corrosion. <br />Now, looking at the picture, it seems that this is the hole for the flapper pivot pin.<br />The boat has run fine for two seasons like this, but since I bought the boat used, is it possible that the previous owner removed the flapper?<br />My OMC factory manual doesn't seem to make any referance to the existance of the flapper, but since a steady stream of water would pour in with the hole open, I'm assuming that the flapper sits below water level on my boat. ( 1986 4 Winns<br />Horizon 3.0 OMC).<br />Any help would be appreciated.<br />John

 

[VMAX]

Re: Exhaust Flappers

This is troubling me now.<br />I discovered a water leak into my bilge coming from a small hole in the exhaust pipe, so I plugged it , thinking that it might have been a hole caused by corrosion. <br />Now, looking at the picture, it seems that this is the hole for the flapper pivot pin.<br />The boat has run fine for two seasons like this, but since I bought the boat used, is it possible that the previous owner removed the flapper?<br />My OMC factory manual doesn't seem to make any referance to the existance of the flapper, but since a steady stream of water would pour in with the hole open, I'm assuming that the flapper sits below water level on my boat. ( 1986 4 Winns<br />Horizon 3.0 OMC).<br />Any help would be appreciated.<br />John

 

[BRIAN03]

Re: Exhaust Flappers

The water leak is from the hole in the exhaust tube for the exhaust flapper. The rubber bellow is not pulled down far enough to cover/seal the hole in the exhaust pipe. The clamps need to be loosened and the rubber bellow needs to be moved down the pipe 1/2 inch and tighten the clamps back up. The exhaust flappers are made of aluminum and covered with rubber. The rubber is removed when the engine is over heated. Mercruiser has redesigned there flapper three times. Mercruiser calls the flappers now (shutters).

 

[notaxnd]

Re: Exhaust Flappers

I have a volvo 3.0 same engine as the OMC that is shown on Boating Bob's web page infact the picture and part numbers are the same as in my shop manual. Anyway I was going to replace the exhust rubber flapper on my engine come to find out volvo have a service bulletin out to remove the flapper and leave it out. It states, Fill the pin holes with silicone,and cover with masking tape and make sure the bellows cover the masked holes. Something to check on it way be the same for OMC.

 

[VMAX]

Re: Exhaust Flappers

I will check with my OMC dealer to find out if they recommend removing or replacing the flapper.<br />The upper elbow of the exhaust is so far above the water line, that I'm not sure how water would ever get into the engine. I have heard stories of exhaust flappers making a rattling sound, so maybe thats why it was removed.<br />Does anyone out there know why someone would remove the flapper?<br />John

 

[denniz]

Re: Exhaust Flappers

Volvo did this on 2000+ year model engines because they had a water injestion problem.The flapper wasnt the problem it was the installation. The 2 rubber grommets were squeezed so tight they hung the shutter. As for there purpose, a good backwash(quick slow down) will thrust water into the manifolds and down any open valve. Usually a shutter will burn from overheat and lodge in the exhaust passage(banana in the tail pipe) Hope that helps. P.S. OMC never removed there shutters. I talked direct to Volvo Tech line and there response was "we never used to use them" TRUE but they did have a shutter on the drive exhaust outlets, and some in the bellows.