What is this piece of metal? (1973 Mercruiser pre-alpha bellows job)

[Campfire]

When I took the stern drive off, this piece was laying inside one of the bellows. Any ideas what it is and if it is important? (Glasses for size comparison)

 

[GA_Boater]

It's part of a destroyed flapper or water shutter that used to live on the top of the Y or 1/2 Y pipe ( Y for V motor, 1/2 Y for inline motor).

The rubber part of the flapper often melts during an overheat. Flapper(s) keep water from backing up the exhaust when quickly slowing and destroying the motor with ingested water. Below is an example of an inline exhaust.

 

[Campfire]

The motor definitely overheated as the plastic bits and impeller were destroyed. Thanks for the ID. I’ll dig into the schematic and find that part. I’m guessing the upper exhaust bellows is rubber, eh?

 

[Campfire]

This is the schematic for my inline Mercruiser 165hp. I see the part number for the flapper. I’ll take a look at the upper exhaust bellows (part #53114) tomorrow.

Any other parts that I should be on the look out for due to an overheat?

 

[achris]

(Plastic) Water pocket cover in the drive shaft housing. If the engine was run long enough to drop the shutter, then that plastic cover is absolutely going to be damaged. And if you don't replace it, you'll get overheats until you do.

 

[Campfire]

Thanks Chris. I replaced the water pocket cover, water tube, and the entire impeller assembly. I took off the exhaust elbow from the manifold and removed the exhaust bellows from that elbow. The bellows didn’t seem to be in bad shape even though it is rubber. As GA Boater correctly stated, that piece was the exhaust flapper.

I’m a bit confused as to what I should be seeing. There is a bar that goes across the mouth of the exhaust elbow assembly (Mercruiser part #53113a2). It is a bit loose and appears to be permanent. Is that what the exhaust flapper attaches to or is that part of the old flapper that disintegrated?

 

[achris]

...I’m a bit confused as to what I should be seeing. There is a bar that goes across the mouth of the exhaust elbow assembly (Mercruiser part #53113a2). It is a bit loose and appears to be permanent. Is that what the exhaust flapper attaches to or is that part of the old flapper that disintegrated?

That was the centre section of the shutter (#7 in your diagram). When you buy a new shutter, you will need to remove the support brackets for that 'bar', remove the bar, and insert the new shutter... I'd replace the screws and nuts too (#3 and #4 in the diagram).

Chris....

 

[Campfire]

Chris, the supports appear to be riveted onto exhaust elbow assembly. I’ll jump back in and check. Thanks for clarifying what that structure is.

 

[GA_Boater]

Does the shutter rod still have the second metal part like the one you found in the exhaust bellows? It may be floating around in the exhaust path somewhere if it is no longer attached to the rod.

 

[Campfire]

GA, I found the second half of the flapper this morning. Thanks for pointing that out. A bunch of burnt black crap fell into the exhaust when I touched the remains of the flapper so I’ll run a garden hose spray through that part. I just need to figure out how to get the old parts out.

 

[Campfire]

It appears this part is actually riveted in. Here’s a listing for a NOS part # 53113A2. I guess I just need to order the flapper and figure out how it goes on.

 

[Campfire]

Crap, they are riveted. https://forums.iboats.com/forum/eng...ives/607859-mercruiser-120-shutter-replacment

I’ll leave the link here in case somebody stumbles on my thread. Thanks for the helps folks!

 

[GA_Boater]

As long as you got the two metal church window looking pieces, the rest is burnt rubber and it will shoot out the exhaust as soon as water and exhaust gas hit the charred rubber.

 

[achris]

If they are riveted, then it's still original from the factory. You cut/grind the rivets heads off and push them out. When you order the new shutter, order the screws and nuts. They replace the rivets.

Chris.......