Have you cleaned and resurfaced exhaust manifolds?

[KM7]

This is on a Ford 5.8 Ltr with an OMC OD.
Have you cleaned and resurfaced exhaust manifolds?

I have a few other posts about this. The motor was running hot but only on the port side exhaust and riser. The engine temp was right in the middle. On removal, there was rust and a partial blockage in the port water hose from the thermostat. I will definitely replace both risers/elbows and the thermostat. I have already purchased the new ones. I have the exhaust manifolds off the engine block.

I know many people on here prefer the most complete/professional/expensive repairs. They recommend replacing anything that shows much wear.

I have been looking for either new manifolds or for Very Clean, freshwater-only replacements. So far, the best I can find are new manifolds available in December.

I can afford to replace everything I want to, but it would be dumb not to refurbish fully usable manifolds.

Another option was suggested by a boat repair shop that says this is what he would do:
1) Connect up a hose to the manifolds and blast out all the loose rust.
2) Capture everything that comes out for evaluation
3) Tap on the manifolds with the water running to loosen more rust
4) Soak the manifolds in Evapo-Rust overnight to loosen more.
5) Clean them up and unspect
6) Take them to a cylinder head resurfacing shop for more cleanup and resurfacing of the gasket mounting surfaces ($80 each)
7) Have them pressure tested
8) Paint with a high-temperature engine paint
9) Reinstall

I'd like to hear from someone who has done this or something like it.
I really don't want to be told what a bad idea this is. I'm sure that many of you would just replace everything for $1500. And that is me doing all the labor. If I can do this for a lot less and a lot sooner. I'd like to try,

So who has a story of refurbishing old exhaust manifolds?

Thanks

 

[Bondo]

Ayuh,.... Your manifolds are Junk,..... the rust you want to clean out, used to be cast iron,.....
The thickness of the manifolds is gone,.... yer playing with fire, 'n you will get burnt,.....
I'm done,..... it's yer motor in yer boat, do what ever you want to do,....
When you dump saltwater into yer motor, destroying it with catastrophic failure, all I can say is, We told you so,.....

 

[Lou C]

Bondo is 100% right
You can resurface ones that have very light surface rust but yours are way past that. Trust us on this.
A new set for mine is about a grand. It is what it is.

here's what it should look like!

 

[Chris1956]

Just so you know, cast iron forms rust very easily, however, the rust helps protect the rest of the metal from corrosion. Clearly this helps only to a point as exhaust manifolds rust out. Blasting out old rust may help clean out the manifolds, however, it also disturbs the rust coating protection to the manifold.

 

[Scott Danforth]

asking the same question in 4 different threads doesn't magically make the rusted beyond service life manifolds suddenly better.

buy new manifolds, go boating.

 

[Lou C]

https://www.marineengine.com/newparts/part_details.php?pnum=BAROMC-1-3852347

 

[Lou C]

When I take mine apart, I will be very interested to see what they look like.
back when I still had the OEM OMC one piece batwing V6 exhaust, I could see the wall thickness getting thinner when I took them off.
So what's the point of saving old manifolds, failure of them, is more or less guaranteed, given enough time in salt water. I recall reading a survey done by someone but quoted by Boat US (insurance company) that by year 8 in salt water, failure is about 80% likely.

 

[KM7]

Just so you know, cast iron forms rust very easily, however, the rust helps protect the rest of the metal from corrosion. Clearly this helps only to a point as exhaust manifolds rust out. Blasting out old rust may help clean out the manifolds, however, it also disturbs the rust coating protection to the manifold.

Good to know. Sounds like removing too much rust could make things worse. The right amount may be to only knock out the loose rust and leave the rest. All this may be moot. I may just replace the manifolds. I've been looking for them in lots of places.

 

[Lou C]

The bigger issue is that the internal walls of the manifold, where the gasket will sit, are just too thin for it to seal. Meaning that the water that should stay in the cooling passage is going to leak down into the center exhaust passage and into the cylinders via an open exhaust valve and cause expensive problems. This is the Achilles heel of all wet joint inboard exhaust systems. And is also why Mercruiser came out with their dry joint system which is a big improvement with respect to avoiding leaks at the joint but still needs to be replaced eventually.

 

[Scott Danforth]

'nuff said.

 

[KM7]

I'm going to replace the exhaust manifolds along with the risers.

I cleaned them out as best I could by connecting a hose and blasting water through them while banging on them with a hammer. I then scrubbed as best I could with rust remover and a wire brush.
I'm not satisfied. I'll get new ones!!

Thanks