Alpha One - non return valve???

[mrsaundep]

Hi,

Engine
Make Mercruiser
Model MCM 140
Serial number 5568367
Displacement 181 CID

Stern drive
Make Mercruiser
Type Alpha 1
Serial number OB656591

After removing the sterndrive from the bell housing, a part dropped out of the sterndrive onto the deck as I carried it into my workshop. I did not see where it came from. I cannot find the part in the mercruiser manual, seloc manual, or on here. It looks like a non-return valve (butterfly flap), and is a similar size/shape to the port where the exhaust bellows fits on, it makes sense to have an N/R valve there, but I cannot work out where to refit it. Help please.....

 

[Bondo]

Re: Alpha One - non return valve???

Ayuh,... It's the exhaust shutter, that belongs at the top of the downpipe...

 

[fat fanny]

Re: Alpha One - non return valve???

It's a exhaust flapper it goes in the top of the Y pipe just below the elbow to prevent water back flowing into the engine

 

[Eric 3.7LX Alpha 1]

Re: Alpha One - non return valve???

Have you been hearing a clattering noise from the back of your engine compartment?

Most Mercruiser Exhaust "Y" Pipes have water shutter valves.
These flapper style valves help prevent water from backing up into the engine through the exhaust system.

When the rubber edges of these flappers wear off, then they make a clattering noise at low RPM's. Yours eventually fell right off. Excess heat from a bad impeller or running the engine out of water without muffs can damage the rubber components in the exhaust system.

 

[mrsaundep]

Re: Alpha One - non return valve???

Hi,

Thanks for the advise, appreciated.

Eric 3.7 - no, there was no abnormal noises/clattering at all.

Can anyone post a sketch or photo of where the flapper should be fitted? I still cannot find it in my manuals??
Tks,

 

[mrsaundep]

Re: Alpha One - non return valve???

Found it! Manual 3, Section 5, pages 5C-5&6. Any ideas why these fall out? And how to prevent this re-occuring when I re-install it?

Tks again.

 

[Don S]

Re: Alpha One - non return valve???

Any ideas why these fall out? And how to prevent this re-occuring when I re-install it?

The fact that it's held in with pop rivets, and living in a hostile environment for almost 25 years has something to do with it. Overheats can also cause the shutters to become brittle and fall apart.