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Exhaust flappers
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Author:  Taza [ Wed Apr 23, 2014 12:11 pm ]
Post subject:  Exhaust flappers

Volvo recommend that not to fit the exhaust flappers,I have a 1997 205 has anyone else done this,

Cheers

Author:  rpengr [ Wed Apr 23, 2014 12:53 pm ]
Post subject:  Re: Exhaust flappers

Yes. I removed them from my OMC Cobra and had no issues. LouC and some other members have removed them also.
edit: LouC replaced his after they melted once.

The problem with them is: if you get a raw water blockage (such as a plastic bag over your intakes), the flappers melt and get caught in the bottom of the exhaust y-pipe.

Author:  LouC [ Wed Apr 23, 2014 2:46 pm ]
Post subject:  Re: Exhaust flappers

I had to replace them because they melted when I had the overheat last summer. I did replace them but for sure I can't say if they are needed or not. OMC thought they were and I guess Volvo decided they were not, but Merc still installs them. It probably varies from boat to boat depending on how high above the static water line the risers are.

Author:  Graham R [ Wed Apr 23, 2014 4:18 pm ]
Post subject:  Re: Exhaust flappers

There is actually a VP technical service bulletin that recommends to remove them ! I thought I had a copy, but it seems to have disappeared. From memory, it just states to stick some sealant on the flapper shaft holes and refit the hoses. I had a 1999 225 with the 5.7, no flappers from new, no water ingress.

Edit; found the link to the document

http://www.marinepartsexpress.com/jpg/Flapper%20Parts%20Bull.jpg

Author:  Lakebum [ Thu Apr 24, 2014 8:26 pm ]
Post subject:  Re: Exhaust flappers

just pulled our's for bottom paint and some other maintance. Noticed one of my exahaust boots was shot, don't remember ever overheating but it might have just been time. As I changed the exhaust boot I found parts of the flapper in the outdrive exhaust port.
I've read the VP bulletin, so looks like I will be running a flapper on the starboard and nothing on the port.
I think as long as you don't come off of plane to fast and don't beach the boat where water can push up into the ypipe, you should be fine.

Author:  rpengr [ Fri Apr 25, 2014 8:50 am ]
Post subject:  Re: Exhaust flappers

Lakebum wrote:
just pulled our's for bottom paint and some other maintance. Noticed one of my exahaust boots was shot, don't remember ever overheating but it might have just been time. As I changed the exhaust boot I found parts of the flapper in the outdrive exhaust port.

It is possible to burn the exhaust rubber parts without overheating the engine:
1. Weak raw water impeller could supply enough water to keep the engine at normal temperature, but not have enough flow to keep the exhaust rubber parts cool enough.
2. Rust or other blockage in one exhaust manifold will cause more water to flow out the other manifold. Therefore engine temp is fine, but one manifold gets too hot.
3. Rust or blockage in a passageway of the thermostat housing could do the same as #2.

I would try to determine the cause of the damaged boot. It might be time for new manifolds.
Lakebum wrote:
I think as long as you don't come off of plane to fast and don't beach the boat where water can push up into the ypipe, you should be fine.

Coming off a plane could never allow water up the pipe...if the engine is running. But I worry a little about those times when several people are on the swim platform and you get hit by waves (with the engine off).

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