Exhaust Manifold flange worn out

Good evening all,

I'm in the middle of a full restoration of a 1967 Pearson Vanguard and am doing a good bit of work on the engine. I've found that the flange on the exhaust manifold is eaten away on the lower half and is not any where near flat. Obviously from water intrusion over a period of time and due to its location in the engine compartment its almost impossible to inspect while in the boat. I've read a lot of posts and am building a post-exhaust-flange assembly that should keep water out of the manifold but my question is this... How do I 'fix' the degraded flange on the manifold.
1. Replace with manifold from Don (and Co)?
2. Have welder build it back up and then turn it down + re-tap the bolt hole.
3. Other ideas?

As always thank you for your input and advice!

John

[rigspelt]

Can you get the old flange off the old manifold, clean up the manifold and use it with a new MMI flange, or is the manifold's flange mating surface corroded?

I'm ordering a new exhaust flange from MMI. The flange surface on the manifold is what's giving me the problem. The lower portion is very corroded.
John

[sastanley]

John,
I rebuilt my 'hot section' this winter (actually everything except the muffler itself was replaced), and replaced the original flange which was pretty thin with the part that Don sells here. It worked great.

I found that I had some corrosion on the tail end of the manifold as well. Mine was caused from a leaking water hose just forward of the flange, dripping down. I cleaned up the area and used No.2 Permatex in addition to the fresh gaskets. I also replaced the oversized hose and installed the proper size barb to take care of the leaking water.

[msauntry]

In the grand scheme of things, a new manifold would be a good investment since its one less thing to repair in the future. While you've got things accessible and torn down now, I'd say slap in a new one and be done with it.

[sonador]

I've pulled the engine from my boat this winter to do a partial rebuild. I have the same problem with my manifold. I'd taken it to a machinist to have the exhaust end shaved flat, but he thought there wasn't enough metal left to chance it. He suggested building the bad section up with JB weld. I did this by cleaning and scarring the worn away area, then putting the new exhaust flange in place with some wax paper between the flange and the manifold. I pushed the JB weld in build up the missing areas, waited for it to harden, took off the flange and dressed flat with sandpaper. I have high hopes for this repair. The exhaust pressure at this point shouldn't be more than a couple psi and the JB weld should be OK at the expected temperature. One last note; I wouldn't replace the manifold before trying to repair. It's easy to get the manifold off the engine even when it's in the boat (or at least my Catalina 30). It's an expensive part - I'd try to fix it.