How do I inspect/ replace exhaust flappers?

[KD4UPL]

I've got a '97 Mercruiser 5.7 with an Alpha 1. It's got a 2 barrel carb. if that matters. I want to make sure my exhaust flappers aren't burnt or melted. Where are they and what's the easiest way to gain access? Do I remove the manifolds or are they further downstream? What else should I inspect while I've got things opened up?

Thanks,

 

[tpenfield]

About 1/2 down the exhaust tube as it lead to the bottom of the transom assembly . . .


Old/missing one . . .

New one installed

Gotta take the upper part of the exhaust tube off to get at them

 

[achris]

Remove the exhaust elbow from the manifold, remove the 90 degree elbow from the top of the Y-pipe and peer in....
Once you're done, you will need to put new elbow gaskets on, so make sure you have a) the right gasket (there are 3 different gaskets), and b) you install it the right way round (yes, there is 3 wrong ways, and one right way)....

 

[KD4UPL]

I finally got the boat out and inspected the port side exhaust flapper. It looks great. I really didn't see anything that looked like a gasket between the manifold and the elbow. It just looked like two machined surfaces held tight together by 4 bolts. Is the gasket a really thin metal one that was possibly stuck really good? I just stuck it back together.
If one exhaust flapper is good I must assume the other is okay too but maybe I should check anyway. I'd like to get the gasket thing figured out before I tear the other side apart. Did some of these engines not have a gasket? Anything wrong with just putting it back together if it doesn't leak? What would it leak? Exhaust, water, inside, outside, etc.?
Thanks,

 

[stonyloam]

If it is closed cooling, could be. See A here. https://www.mercruiserparts.com/Sho...=EXHAUST+MANIFOLD+AND+CAST+IRON+EXHAUST+ELBOW

 

[KD4UPL]

It's not closed cooling. It runs lake water thru the engine.

 

[stonyloam]

OK, then according to the diagram, for a 97, 5.7 you should have a gasket #5 that looks like this https://www.mercruiserparts.com/showSpecialPicture.asp?pn=863724 I could be wrong, just going by the diagram.

 

[Bondo]

I finally got the boat out and inspected the port side exhaust flapper. It looks great. I really didn't see anything that looked like a gasket between the manifold and the elbow. It just looked like two machined surfaces held tight together by 4 bolts. Is the gasket a really thin metal one that was possibly stuck really good? I just stuck it back together.
If one exhaust flapper is good I must assume the other is okay too but maybe I should check anyway. I'd like to get the gasket thing figured out before I tear the other side apart. Did some of these engines not have a gasket? Anything wrong with just putting it back together if it doesn't leak? What would it leak? Exhaust, water, inside, outside, etc.?
Thanks,

Ayuh,... The gasket surfaces, MUST be Cleaned, before puttin' Anything back together,......

'n Gaskets, Must be used,....

A flat file is My choice of tool for cleanin', 'n flattenin' the gasket surfaces on manifolds, 'n risers,...

 

[KD4UPL]

I guess I need to order some gaskets then. Are these gaskets metal, cork, rubber, what?

 

[stonyloam]

Not cork or rubber, they are a kind of hard composit material, like Your other exhaust gaskets.

 

[KD4UPL]

Well that's interesting, there certainly wasn't anything like that when I took it apart. Weird.

 

[tpenfield]

Well that's interesting, there certainly wasn't anything like that when I took it apart. Weird.

We are talking about the gasket between the 2 heavy iron parts (manifold and elbow) Right? Of course to inspect the exhaust flappers you wouldn't need to take those apart, merely slide the rubber exhaust tube down far enough on the Y-pipe so that you can get the upper exhaust pipe (which looks like an elbow) out of the way, exposing the flappers.

I an wondering if we are all talking about the same set of parts? :noidea:

 

[KD4UPL]

Okay, I "found" the gasket. It seems to be metallic on each side with something soft in the middle. There was a lot of curd and paint that had it stuck to the exhaust elbow. I just thought the metallic surface was the elbow. It had a part number on it so I've got new ones on the way.
Thanks for the help everyone.

 

[Hoosmatroos]

No Title

Yep, replaced mine too last month. Removed the elbows took out the old flappers en replaced them. Old ones were not that bad but I take no risk. And yes, always use new gaskets for the elbows.