Mercruiser exhaust system gaskets.

[ajcampbell31]

Based off of the follow thread, https://forums.iboats.com/threads/mercruiser-exhaust-systems.743405/
I’ve had similar frustrations with aftermarket gaskets, especially in salt water. A while back, I thought the OEM ones would hold up but after a short season, I noticed signs of leakage too. Now I steer clear of the basic fiber types and stick with the stainless/fiber sandwich style, even if they cost more, just for the peace of mind. I’ve been tempted to try making my own with sheet steel but just haven’t found the time. If you’re searching for specific exhaust components or want to see the different gasket and manifold options, you can scope out everything in one place at (Spam removed). They’ve got a ton of alternatives and some decent pricing on hard-to-find marine exhaust parts.

 

[Chris1956]

Have you trued up the manifold to elbow joint? Rust and warped joints can cause all sorts of leaking, even with good gaskets.

A good way to true it up is to use emery cloth on a piece of glass, and "sand" the joints in a figure 8 movement.

 

[Lou C]

I used these on my Barr 2 piece coversion, coated the sealing surfaces with Permatex aviation and no leaks inside....
Endoscope pic after 5 seasons of use in salt water....

 

[Scott06]

Have you trued up the manifold to elbow joint? Rust and warped joints can cause all sorts of leaking, even with good gaskets.

A good way to true it up is to use emery cloth on a piece of glass, and "sand" the joints in a figure 8 movement.

X2 on this check the mating surfaces. Some cheaper aftermarket manifolds are not flat from the factory

And if they are corroded they may need replacement

 

[Lou C]

First thing I did with my Barr conversion. After I took the paint off they were just about perfect…