Exhaust manifold port corroded (Merc 470)

[Max-Falcon]

Hi
I am in process of servicing the head on my Mercruiser 470 and consequently had to remove the exhaust manifold which is an aluminum type. Once out, I found some corrosion on the port number 4 of the manifold. Basically after sanding the corroded flakes, now less than half of the diameter of port 4 is a bout 1/8" lower than other ports (photo attached)

My first thought was to get it to a weld shop and have them build up the lip, then send it to machine shop to plane it. But all the welding shops so far refused to do this job, either by saying straight NO or just quoting an unreasonable cost (one of them said at least $1000!)

I am now wondering if there is a quick and dirty DIY remedy for this. I have looked into High temp jb weld, exhaust repair tapes, flux blazing etc. Anyone has had similar experience? Also how hot the surface of the manifold gets right at the head port connection? and if this port leaks a little bit what issues am i going to face?

 

[Coastiebrewer]

Not real familiar with that engine, but I'd shy away from trying to JB weld it (or similar). In general, the exhaust system tends to be quite hot, so the stresses don't take well to added material.

You might check and see if you have room to have the manifold "decked". Think how a machine shop re-machines a head to ensure the mating surface is precisely straight to seal the head gasket. They may be able to do a similar procedure for the manifold mating surface. You just need to make sure that you don't have alignment issues if they take material off of all the ports.

Anybody else have any thoughts?

TLDR; I don't recommend JB weld for this. Consult a machinist familiar with the engine.

 

[Scott Danforth]

You need to get it welded, or buy a new manifold. Exhast gassed are up to 1300F....no way JB weld will hold.

Your local radiator shop welds aluminum every day

 

[Max-Falcon]

You need to get it welded, or buy a new manifold. Exhast gassed are up to 1300F....no way JB weld will hold.

Your local radiator shop welds aluminum every day

Buying a new manifold wouldn’t make economical sense to me! It’s about 2 grand! Specially when other than that little corrosion my manifold is in great shape.

I’ll call more weld shops and radiator repair shops thou.

But check out this High heat JB weld, they claim it is good for up too 2400 degrees Fahrenheit! It literally advertises that it is “great for exhaust manifolds” I know the actual exhaust gases are very hot but does the actual manifold surface get that hot? Aren’t boat manifolds cooled with coolant? I saw a bunch of YouTube videos where the car exhaust pipes were fixed by jb weld and such!

 

[Scott Danforth]

those flanges are not cooled, only the main body. get it welded.