Anybody Have Any Luck Epoxying Exhaust Manifold Surfaces?

[San_Diego_SeaRay]

1998 Merc 7.4 Bravo

One cylinder had a stuck valve due to manifold failure/water intrusion into exhaust ports. So I took off both of my heads and brought them to a machine shop. After jet cleaning, they say overall the heads look in pretty good condition. The major issue is that a few of the oval exhaust side ports have heavy pitting around the edges. The worst one actually doesn't have any sharp edges; just rounded inward. I'm gonna talk to the "main" guy tomorrow to see how we move forward.

So my thought is that they've started to make (or they've always made but I didn't know about it) exhaust muffler epoxy that fixes exhaust leaks. It's an epoxy putty that can withstand 1000+ degree temps. The specific one I'm thinking about is Blue Magic Quik Steel, but I know Permatex also makes something similar and there are still others.

Has anybody ever layed down some of this stuff to smooth out pitting? My thought would be to lay a thin coat, then wax paper, then bolt down the manifold on it and let it cure over night. Next day file down the excess and re-install the manifolds w. the gaskets.

Experiences? Thoughts? Or other suggestions?

I guess the worst thing is an annoying exhaust leak...

 

[Scott Danforth]

you do realize that the exhaust of a big block can be 1200 degrees.

if this is your exhaust manifold surface, buy new manifolds

if its your head, have it welded and dressed off.

 

[QBhoy]

Just get new ones. They are a “consumable” part.

 

[wingless]

It sounds like this is a salt water boat w/ raw water cooled exhaust.

If so, the exhaust needs to be disassembled for an annual inspection for excess raw water passage corrosion and for sufficient SOLID wall thickness between the raw water passage and exhaust gas passage, w/ replacement when parts deteriorate to unacceptable condition.

The OEM raw water (salt water) cooled manifolds, risers and elbows would last 3 to 4 years on my boat before I was unwilling to continue usage of those parts. I then redesigned my exhaust from unable to flush and unable to drain the raw water circuit, to now drain, fresh water flush, soapy water flush, Salt Away flush, then drain bone dry after every usage.

My latest disassembly for internal inspection, after 3 years of usage, reveals the internals of those incredibly expensive cast iron parts to still looking brand new. My expectation is that these parts will now last the life of the boat.

 

[San_Diego_SeaRay]

you do realize that the exhaust of a big block can be 1200 degrees.

if this is your exhaust manifold surface, buy new manifolds

Sorry - I should have been more clear. It is the heads that have the pitting, not the manifolds. The manifolds are going in the trash, so I'm not concerned about those surfaces.

These products are made for high temps. That's why I'm not considering regular JB Weld, which would otherwise sound like a good solution too.

if its your head, have it welded and dressed off.

Hmmm. Good suggestion. This wasn't offered to me by the guy at the machine shop. That's probably why he isn't the "main" guy. I'll talk to him about it tomorrow.

 

[San_Diego_SeaRay]

The OEM raw water (salt water) cooled manifolds, risers and elbows would last 3 to 4 years on my boat before I was unwilling to continue usage of those parts. I then redesigned my exhaust from unable to flush and unable to drain the raw water circuit, to now drain, fresh water flush, soapy water flush, Salt Away flush, then drain bone dry after every usage.

My latest disassembly for internal inspection, after 3 years of usage, reveals the internals of those incredibly expensive cast iron parts to still looking brand new. My expectation is that these parts will now last the life of the boat.

Yes, mine are salt water/raw water cooled. The manifolds are going in the trash. That's quite the routine you've got. I wanna buy your boat when you sell it! My storage area doesn't allow for soapy water flushes as it drains into the marina from the parking area. I've never heard of a set of manifolds lasting the lifetime of a boat but I'm not gonna bet against you and your meticulous efforts.