SS Vs Black Iron Exhaust Elbows

[S/V Alchemy]

Originally Posted by kmacdonald

I don't like the elbow designs that will leak salt water into the engine exhaust ports when the elbow fails. All the manufacturers seem to favor a design that destroys the engine in the event of elbow failure. I like a dry exhaust manifold, a riser to the highest point in the engine box, a loop, a y-fitting and water injection on the downward side of the loop. I wrap it with lagging. It's a fail safe design, less than $75, and easy to make and install. The price difference between SS and black iron isn't much but if I use SS there will be a joint of SS and black iron somewhere and that causes me concern. 15+ years out of SS sound like a winner though.

Good, but can be improved further with an EGT or water flow sensor if you suck in a bag in the raw water circuit or the impeller throws some vanes, etc. Your design fixes water backing into the manifold, but doesn't solve failure of the cooling circuit. I'm redoing my exhaust (post-water injection, post waterlift) to "T" into two exhaust hoses either side of the boat, meaning I can actually get rid of the anti-siphon plumbing. It will look like this (copyright Dave Gerr, btw) and yes, that 9 inch differential is the key:

[S/V Alchemy]

Originally Posted by Jim Cate

...

I've never understood why Yanmar uses those loop type exhausts... they seem to be a frequent cause of trouble, and Yanmar views them as consumables (profit motive?)

Jim

Probably. Conceptually, thinking about getting water out of the boat via the exhaust from around the waterline efficiently and without creating too much heat or back pressure has been one of my greatest challenges as a sailor. I'm glad I'm not working in a typical engine bay under a set of stairs and can get at everything and have some vertical space to simplify. The original question of mixing elbow materials is nearly secondary to me because of this: as you point out, a bodged up fabrication made by you worked well enough for long enough to justify the small amount of work it took. The important part was probably thinking about where the water would be when motoring on a heel or when the engine failed to catch immediately. I know I care not to ever again do a kerosene flush, and will labour hard to avoid that.

[sailorchic34]

Ah SS or iron, A toughie. Myself I would stick with the iron (or plain steel) elbow. First my old elbow lasted over 20 years. Second and more importantly Iron (-0.65v) is a anode to Stanlass Steel (-0.1v) which is a fairly high potential differential, so there is some worry in my mind that there could be galvanic corrosion in say the iron block or steel threads. Probably not a biggy, but the Potential (pun intended) is there.

Of course, the gasket between the elbow and block would reduce issues, though threads might still get ate over time.

[kmacdonald]

Originally Posted by S/V Alchemy

Probably. Conceptually, thinking about getting water out of the boat via the exhaust from around the waterline efficiently and without creating too much heat or back pressure has been one of my greatest challenges as a sailor. I'm glad I'm not working in a typical engine bay under a set of stairs and can get at everything and have some vertical space to simplify. The original question of mixing elbow materials is nearly secondary to me because of this: as you point out, a bodged up fabrication made by you worked well enough for long enough to justify the small amount of work it took. The important part was probably thinking about where the water would be when motoring on a heel or when the engine failed to catch immediately. I know I care not to ever again do a kerosene flush, and will labour hard to avoid that.

I always take the exhaust loop as high as possible in the space available. That's the best that can be done without major surgery. If that loop happens to be higher than the exhaust gooseneck just prior to the exhaust exit, then no anti-siphon valve is required in the water injection plumbing.

[jhulmer]

I have just gone through all this myself in the process of repower during a refit.
I looked at all the information I could find and (because of ease of fabrication) most custom exhaust risers are fabricated out of Stainless steel. I chose 316L but I have seen some made out of 309 because it handles the heat better. However, those were on larger engines.

My new Yanmar came with a stainless mixing elbow so I have to assume they have moved away from bronze and aluminum.

Here is a good website to look at: https://www.sbmar.com/articles/every...haust-systems/

Picture of my completed riser and mixer:

[Compass790]

Definitely ss. I have made a few over the years using both TIG & stick welding. If i can attach a photo of latest I will but I'm no 'puter geek.
My recommendation is use Schedule 10 316 ss pipe as it's readily availiable & lasts way longer than tube & you can stick weld it so easier for the average guy to make at home. Dont have to purge with argon either but i recommend pickling where possible. As others mentioned better to put the water injection on downstream side so you dont put water on top of exhaust a la Yanmar if it has problems. Bronze sounds nice, havent tried that, but imagine procuring materials would be a PITA.
The one pictured ( If attachment works !) used threaded elbows but better if you can get welding ones but threaded will wrk too.I used ceramic wrap up to injection point, great stuff but silcone sounds intriguing.

[bauer965]

Hi.
I had a riser rebuilt many years ago, that is essentially the same as depicted by jhulmer. I'm telling you, this is likely the way to go.
One difference from mine, my fabricator made the "up" portion out of mild steel, and the "down" portion out of SS (and my "down" portion is a bit longer). A proper weld joining the two types poses no concern. I suspect the fabricator did this to not only save costs, but to maintain similar metals at the engine connection. Which was a good thing, because I actually re-used it when I repowered to a new Westerbeke which required me to cut off the old flange and weld on a "turbo-style" V-clamp fitting...child's play for any competent welder.
Observations:
1. I've inspected this riser several times, and have identified no ill effects.
2. I used fiberglass wrap for insulation as shown by jhulmer, and can attest that you can put your hand on this while operating.
3. Mine also doesn't have the short section of jacketed pipe on the down pipe...the water just enters at an steep angle. Again, I've seen no ill effects.
4. I've had a few other mechanics take a look at the riser (including the Westerbeke rep who would have rather sold me a $350 Westerbeke riser), and they all seem to appreciate it's workmanship and adherence to design requirements.

Hope this helps, I know some is duplicative, but just wanted to give a "second" to the jhulmer design.
Erich

[dneve]

After 32 years of use, my Perkins 4-108 iron exhaust elbow developed a leak so I replaced it with the same elbow which points downward so no water entered the engine. No problem with clogging either.

[stnick]

I have used The black iron on my Sabre The SS from volvo was almost 500 dollars
so i made one from home depot black iron. Than I had the inside ceramic coated by a local shop. I had it some 10 years and would take it apart every 3 years or so and there was no rust . For what it cost in my view the ceramic coating on the inside saved the black iron.

[Jim Cate]

Originally Posted by stnick

I have used The black iron on my Sabre The SS from volvo was almost 500 dollars
so i made one from home depot black iron. Than I had the inside ceramic coated by a local shop. I had it some 10 years and would take it apart every 3 years or so and there was no rust . For what it cost in my view the ceramic coating on the inside saved the black iron.

What specific ceramic coating did you use, and what kind of costs are we talking about? Sounds interesting, even if applied to an OEM part to increase MTBF.

Jim

[Schooner Chandlery]

Originally Posted by Jim Cate

What specific ceramic coating did you use, and what kind of costs are we talking about? Sounds interesting, even if applied to an OEM part to increase MTBF.

Jim

The ceramic coating does sound intriguing. I favor mild steel and black iron over stainless for boat exhaust fittings.

I should not admit the mix-match we have upon our boat but here it is -- the original mild steel nipple exiting the Cummins 5.9L engine exhaust manifold that has a flange is what we started with. We bolted on a custom fabricated stainless flex section (sloping upwards away from the engine) about 12" long. This has a flange to a tortuous section of pipe fittings and nipples that defy reality but were necessary to provide maximum rise and deal with the particular location of that rise which included getting around a structural member of the boat -- two 45 elbows and the 90 degree injection elbow among them (it is at the topmost level) and then post-injection we have exhaust HOSE going down into a Vetus waterlock/muffler which sadly is set not as low as we'd like but at a minimum distance below the engine height (don't recall what it was but we were at absolute minimum recommended height differential) and then a 8' long long section of exhaust hose slowly rising to exit the transom. At the transom, we have a shutoff valve and another riser and 180 at the top (two elbows) and short pipe down to a 90 that exits the boat. The 180 at transom was to prevent water to backpush into the exhaust system. All metal components near engine are mild steel and at transom are bronze (we happened to have access to some high quality bronze pipe fittings when rebuilding the boat). All were installed in 2008 and still with us, knock on our wood hull, they will hopefully last quite a bit longer. My husband and I go back and forth about the wisdom of breaking open the system to check the condition of the Rube Goldberg elbow configuration. Those mild steel fittings are very inexpensive and I was advised by a diesel mechanic friend to simply replace them every few years. Of course what "few" accounts to is up to the user to interpret.

I'd be keen on a ceramic coating though -- it could turn my "few" years into decades I'm thinking.

[a64pilot]

Ceramic coated automobile headers are miracles.
Used to be they would rust in days, ceramic coated ones never do.
I’d have it ceramic coated inside and out.