Merc Manifolds and Risers... To Perfect Seal or not to Perfect Seal...

amajamar

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Mar 18, 2014
Messages
24
...that is the question. Again.

I have read the Service Bulletin from Merc about the "new" graphite gaskets, circa 2001, that are to be installed dry. However, a search on this site and many others has turned up multiple posts from boat owners and marine mechanics who use Perfect Seal on those graphite gaskets. To me, it seems illogical to put a sealer on a soft surface like graphite, however, as I am about to undertake the procedure myself, I would like to ask again for clarification. I want a leak free installation, however, part of my confusion stems from not really being sure how the graphite gasket works anyway. Does the graphite bond to the metal (or more accurately, painted metal of the new parts)? Why does dry graphite create a better seal than all the myriad gasket materials and sealants that came before it?

In any case, I would like to have the conversation one last time before I undertake the reinstallation process, just to be sure.

Thanks in advance!
 

Bondo

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70,468
Re: Merc Manifolds and Risers... To Perfect Seal or not to Perfect Seal...

...that is the question. Again.

I have read the Service Bulletin from Merc about the "new" graphite gaskets, circa 2001, that are to be installed dry. However, a search on this site and many others has turned up multiple posts from boat owners and marine mechanics who use Perfect Seal on those graphite gaskets. To me, it seems illogical to put a sealer on a soft surface like graphite, however, as I am about to undertake the procedure myself, I would like to ask again for clarification. I want a leak free installation, however, part of my confusion stems from not really being sure how the graphite gasket works anyway. Does the graphite bond to the metal (or more accurately, painted metal of the new parts)? Why does dry graphite create a better seal than all the myriad gasket materials and sealants that came before it?

In any case, I would like to have the conversation one last time before I undertake the reinstallation process, just to be sure.

Thanks in advance!

Ayuh,..... Welcome Aboard,.... Ya supposed to clean the Paint off the gasket surfaces,....

All gasket surfaces, All the time, get cleaned to Clean Smooth Metal,...

As for usin' Perfect Seal,.... Ya, I use it on threaded fasteners, like never-seize, to keep 'em from gettin' rusted, 'n stuck,...

Much Better than never-seize for applications like that,....
another trick DonS taught me,.... ;)
 

amajamar

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Mar 18, 2014
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Re: Merc Manifolds and Risers... To Perfect Seal or not to Perfect Seal...

Ayuh,..... Welcome Aboard,.... Ya supposed to clean the Paint off the gasket surfaces,....

All gasket surfaces, All the time, get cleaned to Clean Smooth Metal,...

As for usin' Perfect Seal,.... Ya, I use it on threaded fasteners, like never-seize, to keep 'em from gettin' rusted, 'n stuck,...

Much Better than never-seize for applications like that,....
another trick DonS taught me,.... ;)
OK, so no Perfect Seal on graphite gaskets. So what's the best way to remove the paint on all the new parts??
 

NHGuy

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May 21, 2009
Messages
3,631
Re: Merc Manifolds and Risers... To Perfect Seal or not to Perfect Seal...

I use a surfacing disc in a cheap angle grinder. They are little discs made with scotchbrite abrasive. Just use them in such a way to avoid rounding off any of the flat surfaces.
 

pyrotek

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Nov 19, 2011
Messages
183
Re: Merc Manifolds and Risers... To Perfect Seal or not to Perfect Seal...

I had the same question a few years ago when I was doing the same job. Have you received and looked at the OEM gaskets? I think once you see them and have them in your hand, they are relatively "soft" compared to the heavy metal risers and manifolds and you can invision how they will clamp together to form a nice seal. Therefore I didn't use anything and no regrets. I think with any kind of gasket sealer, it is difficult to ensure a uniform seal if its not done carefully. I'm sure it can be done, but may increase the likelyhood of a bad installation. That's my theory.

Are you using OEM or aftermarket gaskets? Highly recommend OEM.
 

amajamar

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Joined
Mar 18, 2014
Messages
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Re: Merc Manifolds and Risers... To Perfect Seal or not to Perfect Seal...

I use a surfacing disc in a cheap angle grinder. They are little discs made with scotchbrite abrasive. Just use them in such a way to avoid rounding off any of the flat surfaces.

I take it you mean the 3m Roloc coarse 2" discs? Will that take off the paint relatively quickly?
 

amajamar

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Joined
Mar 18, 2014
Messages
24
Re: Merc Manifolds and Risers... To Perfect Seal or not to Perfect Seal...

I had the same question a few years ago when I was doing the same job. Have you received and looked at the OEM gaskets? I think once you see them and have them in your hand, they are relatively "soft" compared to the heavy metal risers and manifolds and you can invision how they will clamp together to form a nice seal. Therefore I didn't use anything and no regrets. I think with any kind of gasket sealer, it is difficult to ensure a uniform seal if its not done carefully. I'm sure it can be done, but may increase the likelyhood of a bad installation. That's my theory.

Are you using OEM or aftermarket gaskets? Highly recommend OEM.

Yes, I am using the OEM graphite gaskets.
 

HT32BSX115

Supreme Mariner
Joined
Dec 8, 2005
Messages
10,083
Re: Merc Manifolds and Risers... To Perfect Seal or not to Perfect Seal...

Howdy,

This is mainly for others that it might apply to.....

Since you didn't mention engine type or model number, if you need new manifolds and can switch to dry-joint type manifolds and risers at your next manifold/riser replacement time,

You'll eliminate the need for riser gaskets and worrying about riser gasket leaks for ever.

Regards,


Rick
 

Bondo

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70,468
Re: Merc Manifolds and Risers... To Perfect Seal or not to Perfect Seal...

I take it you mean the 3m Roloc coarse 2" discs? Will that take off the paint relatively quickly?

Ayuh,... If yer usin' the Coarse ones, be gentle, yer only removin' the Paint,...

'ell,... a green kitchen scrubbin' pad, by hand, will get the job done,... just more work,...
 

amajamar

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Joined
Mar 18, 2014
Messages
24
Since I was the original poster, I will bring this thread back to life with the following comment/question...

I installed the new manifolds and risers with the gasket installation technique indicated in this thread... remove paint from mating surfaces, install Merc gaskets dry, and torque properly. After running the engines, I retorqued appropriately. After winterizing my engines, I removed the exhaust system to make room for general maintenance and cleaning. At that time, I curiously sent my video scope down the elbow exhaust and I was surprised to find evidence of a small amount of rust in all four sets. So I found that all my effort and care to install to manufacturer specs was for not. I'm not sure where I went wrong...

I would like to replace the gaskets this spring. I would also like them not to leak. I know this was a PerfectSeal discussion, however, is there a different gasket material that can be used with some other sealant, possibly some RTV or the like? I know on some V.P.s there was a modification to the install spec to use a copper based sealer, however I don't know if they were graphite gaskets to begin with.

Anyway, any advice would be hugely appreciated.

Thanks.
 

Bondo

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Since I was the original poster, I will bring this thread back to life with the following comment/question...

I installed the new manifolds and risers with the gasket installation technique indicated in this thread... remove paint from mating surfaces, install Merc gaskets dry, and torque properly. After running the engines, I retorqued appropriately. After winterizing my engines, I removed the exhaust system to make room for general maintenance and cleaning. At that time, I curiously sent my video scope down the elbow exhaust and I was surprised to find evidence of a small amount of rust in all four sets. So I found that all my effort and care to install to manufacturer specs was for not. I'm not sure where I went wrong...

I would like to replace the gaskets this spring. I would also like them not to leak. I know this was a PerfectSeal discussion, however, is there a different gasket material that can be used with some other sealant, possibly some RTV or the like? I know on some V.P.s there was a modification to the install spec to use a copper based sealer, however I don't know if they were graphite gaskets to begin with.

Anyway, any advice would be hugely appreciated.

Thanks.

Ayuh,.... How 'bout you take 'em apart, 'n See why they leaked 1st,..??

The carbon/ metallic gaskets from Mercruiser need No sealants of any kind,...

My 1st guess is, the gasket surfaces of the manifold or riser is Bad,....
 

amajamar

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Joined
Mar 18, 2014
Messages
24
Ayuh,.... How 'bout you take 'em apart, 'n See why they leaked 1st,..??

The carbon/ metallic gaskets from Mercruiser need No sealants of any kind,...

My 1st guess is, the gasket surfaces of the manifold or riser is Bad,....

Understood. I am planning on looking in there again over the next couple of weeks, weather depending. I am just trying to get an idea of how to proceed when I find that it is leaking. I'll need a way to get these sealed up regardless of what I find, other than if there is some major problem with all the cast iron I just replaced last spring.
 

Lou C

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Nov 10, 2002
Messages
11,802
I have never liked this aspect of inboard exhaust design. Mercs dry joint is a good alternative. I have the one piece OMC V6 units and I've never had anybwater in the engine. They are NLA so when I re power I may pony up for the Hi Tec Marine one piece stainless units. They cost 2x as much but no joint to leak and here in the salt pond will last 2x as long...
 

Fishermark

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Oct 19, 2003
Messages
5,617
Instead of the scotch brite pads, I have always used a flat fine metal file. It will not only remove the paint, it will also show you if you have any "dips" or other irregularities on the mating surfaces. It will give you a nice, clean, shiney, smooth surface. Exactly what you need.
 

crazy charlie

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May 22, 2003
Messages
5,352
I always use /permatex "Hi Tack" on my riser to manifold surface.It sprays on to the gasket ,both sides and tacks it all together.It is a thin film sprayed on and kind of seals/glues it all together.Comes apart fairly easy too.Never an issue in 30 years.Charlie
 

amajamar

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Joined
Mar 18, 2014
Messages
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I always use /permatex "Hi Tack" on my riser to manifold surface.It sprays on to the gasket ,both sides and tacks it all together.It is a thin film sprayed on and kind of seals/glues it all together.Comes apart fairly easy too.Never an issue in 30 years.Charlie

You use it on the Merc graphite gaskets? Or another type?
 

JIm Cook

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Apr 7, 2005
Messages
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My 1996 7.4L showed a little rust at the gaskets in 2001. Tell tale sign of trouble so I panicked. I don't think they were the newer graphite type from Merc at the time it was built. I replaced them with graphite and used Permatex. Sold the boat to my brother, so I get to do repairs. We opened up the joints last week and no rust or corrosion at the mating surfaces and this is 2015. Still running like a champ.
 

JIm Cook

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Apr 7, 2005
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And I have read that the dry joint exhaust system is not available for the Chevy big blocks.
 

Bondo

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Antique Thread alert,...

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