Buildup in exhaust manifold

[hd002e]

After burning through two exhaust hoses, we pulled the exhaust manifold to find out that the inside diameter is greatly reduced and the raw water passages completely blocked off. I believe it is due to years of saltwater leaving sediment as it gets sprayed onto hot metal. This sediment is rock like and very hard to break off. I am chiseling away at the big chunks but not sure how I will get it out of the water passages that are narrow and somewhat hidden if you don't know where to look for them.

Any ideas on how to clear the buildup chemically? I have tried leaving the whole part in CLR (Calcium Lime Rust) solution but it didn't do much. I may have to get a brand new one but feel like there should be some chemical that will dissolve the buildup without attacking the metal.

Thank you!

[Wotname]

I have found that muriatic acid is very good at dissolving raw water scale build up in cast iron engines so I reckon you could try it on your exhaust, assuming it is steel not some alloy.

Don't leave it too long (say 30 to 60 minutes) and rinse very well after. Try say 20%...

[Captsteve53]

All marine Risers have a limited life (3-5 years) is the recommended replacement (I personally would rather say case by case) that said it shows they indeed a normal replacement part,

Dont forget if some of that Carbon/corrosion comes of during your first hard run it can let sea water enter your lovely newly re built engine(is it worth the risk?) (Just being the Devil's advocate!)

There are quite a few replacement Stainless Steel ones on the market, but mainly manufactured from 304 grade (which dosent like hot sea water!) at the least i would recommend 316 grade (Harder to find) and the very best designed
for hot sea water Stainless 321 Grade (Even Harder to find)

Just a small note on using Muriatic Acid (or by it's other name Hydrochloric Acid) is very strong and if using Please Note when diluting Always pour the acid into the Water (Water into the Acid can be VERY Risky move!)

Cheers Steve

[jamhass]

You can clean this up electrolytically.

Take a 5-gal bucket, water, some baking soda, a 12-volt battery charger, a piece of old steel and a length of PVC pipe.

Here is a link for details:

Rust Removal Using Electrolysis

Note, since you will be removing rust and crud from the INSIDE of the elbow, surround the rebar anode with a piece of PVC pipe to avoid a short circuit. Drill the PVC with lots of holes to allow current and electrolyte to flow freely between the two.

This has worked exceptionally well for me on several occasions, and completely avoids the risks inherent with strong acids.

[David M]

Replace it. You have already lost metal off the inner walls regardless of what you do with the old one now. Do not risk your old one leaking, cracking or breaking off completely. Being cheap now could cost you a lot more money later.

I replaced mine with stainless steel exhaust risers 15 years ago. They lasted longer than the previous engines. (My new engines being identical engines).

Additionally, back pressure is really bad for a Diesel. It is much worse for a Diesel than it is for a gasoline engine. Your old riser will no longer have the smooth walls that it did originally.

[Captsteve53]

Originally Posted by jamhass

You can clean this up electrolytically.

Take a 5-gal bucket, water, some baking soda, a 12-volt battery charger, a piece of old steel and a length of PVC pipe.

Here is a link for details:

Rust Removal Using Electrolysis

Note, since you will be removing rust and crud from the INSIDE of the elbow, surround the rebar anode with a piece of PVC pipe to avoid a short circuit. Drill the PVC with lots of holes to allow current and electrolyte to flow freely between the two.

This has worked exceptionally well for me on several occasions, and completely avoids the risks inherent with strong acids.

Would like to make a comment here, The Electrolysis system as above is based on Galvanic Corrosion and stray electrical current corrosion and there's one big hole in that theory (and eventually in your manifold leaving the Carbon in place and here's why:

1) “Carbon” comes from the Latin word “carbo,” which in English means “charcoal.” It is an element represented by the letter “C” and bearing the atomic number 6 on the periodic table.

2)Here's the main point:Carbon is a solid "non-metal" element

3) Since Carbon is a NON -METAL ELEMENT the so called Electrolysis will corrode the iron base (Metallic) but not corrode the Carbon, after corroding the iron base the Carbon may fall away leaving very suspect cavities behind?

Cheers Steve

[boeing1]

suggest replace, tried cleaning one on a friends boat, did not last, no sense doing a dirty job twice.

[Lepke]

A product I use that eats rust, but not good metal is AR5100. You can soak, spray or brush it on. It leaves steel looking like freshly sandblasted metal. It's a concentrate that dilutes 1:16 with water. I've had good luck with other products of theirs, too. About $30/qt.
How long an exhaust system lasts depends on the manufacturer. My Detroit mains have manifolds that look original from the late 1940s. One elbow was replaced before I bought the boat. Engines have 3 zincs.

[Compass790]

I agree with David M & captain Steve, Better to replace with stainless . What I can see of yours looks like a yanmar cast iron one. Quite easy to build your own out of 316ss Sched 10 elbows & pipe or get any place that does ss. welding to do it for you. The metallurgists or welding experts will tell you not to use 316 for exhausts but years of experience tells me it works AS LONG AS YOU DONT USE TUBE. (i.e not the 1.5mm thick stuff) because that can crack. If I could figure out how to post a photo I could send send you an example that I built a fortnite ago.

[Uncle Bob]

Originally Posted by hd002e

After burning through two exhaust hoses, we pulled the exhaust manifold to find out that the inside diameter is greatly reduced and the raw water passages completely blocked off. I believe it is due to years of saltwater leaving sediment as it gets sprayed onto hot metal. This sediment is rock like and very hard to break off. I am chiseling away at the big chunks but not sure how I will get it out of the water passages that are narrow and somewhat hidden if you don't know where to look for them.

Any ideas on how to clear the buildup chemically? I have tried leaving the whole part in CLR (Calcium Lime Rust) solution but it didn't do much. I may have to get a brand new one but feel like there should be some chemical that will dissolve the buildup without attacking the metal.

Thank you!Attachment 155707

Originally Posted by Compass790

I agree with David M & captain Steve, Better to replace with stainless . What I can see of yours looks like a yanmar cast iron one. Quite easy to build your own out of 316ss Sched 10 elbows & pipe or get any place that does ss. welding to do it for you. The metallurgists or welding experts will tell you not to use 316 for exhausts but years of experience tells me it works AS LONG AS YOU DONT USE TUBE. (i.e not the 1.5mm thick stuff) because that can crack. If I could figure out how to post a photo I could send send you an example that I built a fortnite ago.

Hi, am I misunderstanding the question, I read it that the manifold is the problem and the response is to replace it with a stainless steel version, could you please suggest a source for a stainless steel manifold.
Cheers.

[JPA Cate]

hd002e:

What I THINK I see in your hose is normal salt crystal buildup. How we have addressed this in the past is with a muriatic acid solution. Set up the solution in a big bucket, with both the exhaust and the intake routed into it. What you want to do is run the engine, with the acid for a bit. Then turn it off. You will hear it fizzing, and the outside of cooling chambers may warm up a bit. Run it again for a bit. Let it sit.

Repeat till it doesn't fizz any more. If you want to, you could then neutralize whatever's left by letting it suck up a little baking soda and water. This, too, will fizz if there's acid left.

If there is a pencil zinc or two in the manifold, you'll want to remove them before you start with the acid.

Jim used to do this about once a year for the engine we had before this one, which was raw water cooled.

Ann.

[Captsteve53]

Originally Posted by Uncle Bob

Hi, am I misunderstanding the question, I read it that the manifold is the problem and the response is to replace it with a stainless steel version, could you please suggest a source for a stainless steel manifold.
Cheers.

Uncle Bob ,

In Australia here's the link for a stainless unit: https://www.marineenergy.com.au/coll...yanmar-2gm-3gm

Cheers Steve

[Uncle Bob]

Originally Posted by Captsteve53

Uncle Bob ,

In Australia here's the link for a stainless unit: https://www.marineenergy.com.au/coll...yanmar-2gm-3gm

Cheers Steve

Steve, all I can see there is stainless exhaust elbows, not a manifold in sight as far as I can see.

[Captsteve53]

Originally Posted by JPA Cate

hd002e:

What I THINK I see in your hose is normal salt crystal buildup. How we have addressed this in the past is with a muriatic acid solution. Set up the solution in a big bucket, with both the exhaust and the intake routed into it. What you want to do is run the engine, with the acid for a bit. Then turn it off. You will hear it fizzing, and the outside of cooling chambers may warm up a bit. Run it again for a bit. Let it sit.

Repeat till it doesn't fizz any more. If you want to, you could then neutralize whatever's left by letting it suck up a little baking soda and water. This, too, will fizz if there's acid left.

If there is a pencil zinc or two in the manifold, you'll want to remove them before you start with the acid.


Jim used to do this about once a year for the engine we had before this one, which was raw water cooled.

Ann.

Ann, would like clarify a point here (may be I'm reading it wrong?)

Surely you are suggesting running the Muriatic acid through the running engine?

Thanks Steve

[Captsteve53]

Originally Posted by Uncle Bob

Steve, all I can see there is stainless exhaust elbows, not a manifold in sight as far as I can see.

Sorry Bob, thought you were looking at replacing the Riser, (to many names being used I guess?-or may be just getting old,


There's usually no need at all to replace the manifold (unless Aluminium) such as below picture , what material is the 3 GM MANIFOLD,

Cheers Steve