Welding Tips and Tricks

I have some new aluminum marine exhaust manifolds that I am going to weld/seal off the water passages. What would be the best way to remove the factory paint so that it won't interfere with the weld.

Photo and more information would be useful, but if they are cast aluminium, coated with high temperature paint then bead blasting might be your only option.

Sorry. I'm a little slow on computer 'n things.


The area of concern is the top section with the exhaust and water passages. The big center hole is the exhaust passage. The smaller rectangular ones surrounding it are the water passages in the water jacket. I made a SS exhaust system that bolts to this machined surface and I want to seal off those water passages which sometimes leaks into the engine(small-block chevy)

I agree with the blasting suggestion.

I have a sand blast cabinet but that's way too dirty. I presume I have to find a clean bead blaster. There's one at the auto shop but that'd be pretty dirty, too.

Why not just make a spacer out of .125 - .180 stainless and block it with a high temp gasket?
Might save blowing through the manifold.The water ports might be contaminated and not a lot of meat to grind away.
Just a thought.
Gary

That's the stock set up and has always been a point of water an/or coolant intrusion. Marine gas engines rarely wear out. Water getting in the engine from multiple causes are the usual killers and the exhaust system contributes about half of these.