Exhaust Manifold Question

[Rixram]

Okay, something I have been wondering about with exhaust manifolds regarding corrosion:

On every exhaust manifold, there are large hex bolts/screws/nuts on the top and/or sides of them of them. Presumably, these lead to the cooling jacket of the exhaust, and are available for use as ports to add cooling to the different areas...

But if you can plug a threaded hose barb into that felame threaded port, couldn't you add something like this, instead: http://www.jamestowndistributors.com/userportal/show_product.do?pid=350 (example found in a google search of "marine pencil zinc threaded")

That is, assuming you could find the right size to fit the manifold.

If you changed those out monthly (or as required), would that provide a level of corrosion protection to the exhaust manifolds, thus extending the life of the manifold, reducing the risk to major engine failure, etc?

Now, for full disclosure, I'm not a professional mechanic, but I do understand the necessity of protecting my boat against corrosion. I see these ports blanked off (plugged), and for years have wondered why this isn't a regular practice. At some point, somebody had to have tried it...right?

 

[rcknecht]

the cooling jacket wall is not deep enough for that zinc... Pls it would restrict flow. I don't think even if it could be done, the benefit would out weigh the risks...

 

[Rixram]

the cooling jacket wall is not deep enough for that zinc... Pls it would restrict flow. I don't think even if it could be done, the benefit would out weigh the risks...

I didn't mean *that* zinc exactly, but a sort of pencil-type zinc that would fit. I'm not sure on the dimension/clearances, and am speaking in generalities. Specifics can follow after generalities are established. I am looking at this picture, and I see that the 2 side ports would extend into the deep blue sections of this cut-away, meaning it may be possible that there is the requisite room for something to be placed in there:

[URL]http://revolutionmarine.com/shopsite_sc/store/html/media/cutaway480.jpg[/URL][\img]

if the "stock" manifolds have ports on the sides like this unit does: [URL]http://www.marinepartshouse.com/images/photos/large/products_id_18302.jpg[/URL] , then there may be the room.

 

[Rixram]

I think I am tempted to get an old set of manifolds and have a machine shop cut them open longitudinally so I can see how it looks inside for clearances. Unless any of you have tried this already...

 

[rondds]

I'm not so sure the problem is "galvanic" corrosion - more so from just good old fashioned oxidation (RUST!). Those water jackets are cooled by fresh water/coolant on some models and they STILL corrode (albeit at a slower pace).

Crusader puts anodes in their heat exchangers, Merc does not. The Merc system is designed to drain (raw water side) when you shut down. Other than that neither company uses anodes.

 

[Sous]

I'm not so sure the problem is "galvanic" corrosion - more so from just good old fashioned oxidation (RUST!). Those water jackets are cooled by fresh water/coolant on some models and they STILL corrode (albeit at a slower pace).

Crusader puts anodes in their heat exchangers, Merc does not. The Merc system is designed to drain (raw water side) when you shut down. Other than that neither company uses anodes.

Exactly. I'm no pro-wrench, but the anodes help with galvanic corrosion, but manifolds and risers suffer from the good 'ol fashion kind of corrosion.

 

[Rixram]

Exactly. I'm no pro-wrench, but the anodes help with galvanic corrosion, but manifolds and risers suffer from the good 'ol fashion kind of corrosion.

I've had my brain jammed on galvanic corrosion for so long I forgot about regular corrosion. Please pardon me while I clean up my brain-fart.