Mercarb intake gasket

[Jcris]

Hey
I have been trying to figure out what happened to an intake gasket I installed on a 2 barrel Mercarb. (See pic) The intake has a spacer on the flange on which sits a gasket and then the carburetor. Upon inspection of the damaged gasket and the bottom of the carburetor I can’t understand how a new gasket won’t be damaged again. The sealing surfaces don’t match up. Across the center section that separates the two bores the gasket is not supported so it looks like it will just be damaged again. Take a close look at the pictures and please advise me on what I’m missing

 

[alldodge]

The intake manifold is flat, the carb body has a slight bow to it. The carb has a bow and also is missing a piece. Looks like another carb

Edit: wonder if that piece is still in the intake or did it get chewed up and spit out?

 

[Scott Danforth]

wonder if that piece is still in the intake or did it get chewed up and spit out?

long since spit out the exhaust...

 

[Jcris]

Well folks I’m gonna put this gasket in because it makes the most sense, to me.

 

[Scott06]

Well folks I’m gonna put this gasket in because it makes the most sense, to me.

I tried the same on my mercarb (3.0) because originally that oval gasket was more matched to the intake hole than the two hole gasket that was stock on it. Seemed to make more sense but the idle mixture adjustment screw ended acting wonky. Swapped it out for a two hole and it behaved normally when adjusting the mixture. Be interested to see if you have the same experience

 

[achris]

I have a memory of reading somewhere (in Merc literature) that the carb base gasket needs to be the one with 2 holes (one for each venturi), and that a single large hole will cause run problems. Just trying to find the document.

Chris......

 

[Jcris]

Thanks Chris,
if that’s true then how can the center section of the gasket with 2holes be unsupported? I’m just trying to avoid it being ripped apart again. Everything looks right except the base of the carburetor. Everything about the carburetor and motor looks stock. I didn’t notice this issue until I pulled it for inspection. Perhaps this is not the correct lower section of the carburetor. I really doubt it but I’m running out of ideas.
thanks again Chris

 

[Jcris]

And thanks Scott 06
at least someone has had a similar experience. I’m going to continue looking for an answer as I’m in no rush. Got a couple other projects going.
for anyone who may have a mercarb that’s not on a motor a picture of the bottom might help solve this mystery. I do know earlier generations of that carburetor were actually 3 sections with the bottom being the throttle plate. Thanks for the help guys

 

[Jcris]

Alldodge,
What did you mean the carb looks like it’s missing a piece. And it looks like a different carb? What carb?

 

[Fun Times]

+ 3 with achris and Scott06..If you run the bigger gasket mentioned in post number 4, the engine isn't going to run or adjust out correctly... Merc, Past Forum Members and even I have been down that road in the past.

The old/original gasket part number 807982 that you have/show has been superseded to 8079821 and it of a slightly different design and just a bit thicker as I seem to recall it. So I don't think that would happen again...Also your gasket could just be an aftermarket one as well as some carry the same look/design.

There is also one more of the same gasket under the base adaptor., https://www.mercruiserparts.com/bam/.../31515/1937/70

The following are of some photo references of the gaskets for you if desired,
8079821 = https://www.ebay.com/itm/Z42-Quicksi...gAAOSwqxdb2ABe < Notice the date on this package 9/30/09.

807982 = https://www.ebay.com/itm/Genuine-MER...8AAOSw6nhezXTF < Notice the date on this package 5/19/1999.

An aftermarket Sierra (GLM) example, https://www.ebay.com/itm/GASKET-GLM-...cAAOSwOHpcG8WI

To see an image of the bottom of your carb part number 3310-807764A1 , the following site has on for you, https://www.marinecarburetors.com/pr...rcruiser-boats

 

[alldodge]

Alldodge,
What did you mean the carb looks like it’s missing a piece. And it looks like a different carb? What carb?

This piece, and IMO would be the reason the gasket won't hold

 

[Jcris]

Thanks guys,
Excellent information.
It does look like the gasket I used was a poor example. Definitely thinner. The base of the Rochester 2 barrel looks different also. That “missing “ piece you highlighted Alldodge shows a different throttle plate than the Mercarb. So, at this point I’m going to hunt down the thicker version of the gasket and give that a try.
I’m really disappointed that the gasket that came in the kit is not more substantial. I purchased from a reputable source or so I thought. I’m going to reach out to him and see how he responds.
However it goes I think I’m on the right path now. I’ll post results when I get them
thanks again everyone