Exhaust Flapper Water Shutter - Replace it or not?

[RonKrifchin]

Good Morning all,

My boat has a 3.0L 2013 crate motor that has been ignored and abused by it's previous owner(s)! Well it's mine now and I doing some extensive maintenance.

So the the latest adventure with the boat came the other day when I dropped the lower gear housing of the outdrive and I found the remnants of what I think was the exhaust flapper!

The question is, where exactly is/was the valve located and how do I get to it? The boat is on the trailer so I'm not to worried about it sinking, well for the moment if I need to take some critical plumbing apart!

I just replace the head gasket so the exhaust manifold and riser are off hopefully making it easier to replace this valve if necessary...

Any help would be most appreciated.

Thanks,
Ron

 

[Scott Danforth]

the flapper sits in the y-pipe below the exhaust elbow

yes, you need it on a mercruiser. its there to prevent hydrolocking

 

[Bondo]

Ayuh,...... On a 3.0l, it's at the top of the Down-pipe,......

No Y-pipe with an in-line motor,.......

 

[kulle]

Replace them, I found part of mine lodged in my exhaust, which caused me all kinds of shut off issues. They act as a check-valve.