Mercruiser 470 elbow

[aarons 470]

Mercruiser Exhaust elbows, are you guys using any kind of sealant? This elbow has 2 gaskets and plate in-between.

 

[kenny nunez]

A dry fit is usually good enough.

 

[nola mike]

The graphite type gaskets (mercruiser, mallory) seal better than the green paper (sierra). No sealant.

 

[aarons 470]

Ok thanks guys. Reason i asked, I had used small amount of sealant On the bottom gasket where it meets manifold. Slight wear there on manifold. I didn’t seal the rest, after I did it wondering if I should have sealed the other 2. Sounds like I’m ok, but I could remove it and goop others.

I bought gaskets few days back they are the green paper type the shop gave me. I didn’t know there were better versions.

 

[Bt Doctur]

must be something new , the 470 is usually a single gasket

 

[Bt Doctur]

 

[nola mike]

I thought the 3 gasket setup was superseded...I've never seen anything but the single gasket.

 

[aarons 470]

Mine has different elbow manifold assembly Elbow is smaller and farther back. I learned the hard way I picked up the newer elbow manifold package and the elbow doesn’t mate up right to my flapper tube. Different engine cowl and transom pieces etc.

Mine is the 470 mcm if I remember right. It’s he second package they made. My boat is an 82. This diagram is from the service manual. At the shop mechanic there showed me the 3 gaskets on their computer. and sold them to me. Center plate is aluminum.

So I’ll just leave as is unless
you guys think I should seal up all 3. I only sealed one touching manifold. And It did mate up nice.

 

[achris]

The green paper gaskets are notorious for leaking. Pull them off and put the proper merc gaskets on.

Chris....

 

[aarons 470]

I just came in from taking it apart and using rtv on it all torqued up. Ok or rip it apart and change gaskets?
I covered entire surface of gasket nice and smooth
Let it rest before tourqing etc.

 

[achris]

I just came in from taking it apart and using rtv on it all torqued up. Ok or rip it apart and change gaskets?
I covered entire surface of gasket nice and smooth
Let it rest before tourqing etc.

Are you referring to the exhaust elbow gaskets or the reservoir gaskets? Because your photo shows the reservoir off, not the elbow.

Chris........

 

[stonyloam]

He has the “old style” pre 1980 (I think) manifold. Merc still lists it as a three part gasket https://www.mercruiserparts.com/bam/.../30926/1592/60 two gaskets and a block off plate.
the DR’s diagram is the newer style.
Nice looking 470 BTW, like that aluminum valve cover

 

[Scott Danforth]

Ok thanks guys. Reason i asked, I had used small amount of sealant On the bottom gasket where it meets manifold. Slight wear there on manifold. I didn’t seal the rest, after I did it wondering if I should have sealed the other 2. Sounds like I’m ok, but I could remove it and goop others.

I bought gaskets few days back they are the green paper type the shop gave me. I didn’t know there were better versions.

replace the green leakers with mercruiser gaskets or have it leak into your motor and cause hydrolocking

while at it take a flat file and dress the manifold flange

 

[aarons 470]

Chris, it’s the elbow. Thanks Terry, lower image quality photo it’s rustoelum grey color. Does look aluminum in picture so it passes the test!

Does merc make a better gasket for my setup? The other better gasket may only be for the other manifold elbow assembly....

If there’s a better merc gasket and I change it out, what seal is recommended Rtv type, permatex aviation? Currently it’s tourqed at 30 with all surfaces sealed with red rtv gasket maker.

For resovoir piece sealant or just gasket?

 

[achris]

Graphite impregnated composite gaskets go on dry. No sealant at all.

 

[aarons 470]

Just to note the elbow to manifold bolt pattern is different on mine than the newer aluminum one. That’s why I’m wondering if there is a better gasket kit? I’m not finding one.

 

[achris]

Ok, looking at your photo of the manifold, it looks like the cast iron manifold with the early style elbow... Gasket part number is 27-99777-2. There's 2 of them, with a stainless steel plate between them... Look a bit like this....


Chris..........

 

[aarons 470]

Yes, that’s the setup. Gasket pops right up on search with the part number lol. Thanks

 

[Bt Doctur]

Had to dig out manual 3 to find your motor

 

[aarons 470]

I think it’s the mcm 470.