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Old 08-04-2014, 16:56   #1
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DIY Mixing elbow

I have a universal M25 motor with a yanmar style mixing elbow which is all plugged up, corroded and halfway to falling apart. Thought I would try going down the DIY path to build a replacement but am a bit stumped as to how the cost even works out and what parts to buy.

So, my current exhaust has a 1 1/4 street elbow out of the exhaust flange which goes into (I think) 1.5" adpater and then into the yanmar mixing elbow which then outputs the whole product into a 2" (ID) vetus exhaust hose, through the exhuast, around a tree, back down another hole, and two or three mufflers and bends later it shows up out the backside of the boat.

So, I though I would replace the the U shape of the yanmar mixing elbow with two street elbows joined together, then I would add off the backside of the 1.5" wye adapter which I would then step down to put in a smaller injection nipple/hose.

My problem is that none of my home stores stell black pipe or accessories in anything larger than 1". So I looked around at speciality shops but when I added up all these pieces and adapters just to replace the yanmar elbow I was in the range of $130... Well I can buy a new yanmar elbow for not much more expensive than this bunch of hobbled together parts. Am I missing something here? Is galvanized cheaper? What about the fumes, life span, etc?
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Old 09-04-2014, 10:59   #2
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Re: DIY Mixing elbow

If you are going to keep the boat I would go to a stainless steel fabricator and get one made, it's a lifetime job.
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Old 09-04-2014, 12:08   #3
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Re: DIY Mixing elbow

I have built several out of galvanized pipe . When you build it , if it all looks good go back and buy the same parts again for spares . Mine seemed to last 3 or 4 years .
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Old 09-04-2014, 13:38   #4
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Re: DIY Mixing elbow

McMaster Carr (www.mcmaster.com) has a very large supply of plumbing fittings. I'd suggest that you also look at buying weld type fittings, ie elbows, pipe, etc that weld together instead of using threads. They may save you some money. They will certainly be a lighter and more compact assembly. You can get these fittings in 316L stainless.
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Old 09-04-2014, 15:24   #5
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Re: DIY Mixing elbow

Irish Rambler's advice is right on target. Find a good stainless steel fabricator and have one welded up to your specifications. That's what we did in Gaeta, Italy for Euros 100 to replace the Yanmar mixing elbow. That was in early 2011 and it is still like new.
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Old 09-04-2014, 15:39   #6
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Re: DIY Mixing elbow

I dont have the exact cost, but I saw a recent article in a boat mag about building an exhaust elbow from stainless. This was for a Volvo Penta TMD22, but the result was it was a lot cheaper to build from stainless than to buy the part from VP
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Old 09-04-2014, 16:42   #7
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Re: DIY Mixing elbow

When I had a Westerbeke 4-107 I used to use my brother Pistarckle's plan with galvanized pipe. I seemed to get five years out of my pipe pieces, but I was always more successful than my brother and our mother loved me more!
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Old 09-04-2014, 17:34   #8
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Re: DIY Mixing elbow

Thanks for the tips. Thinking more about just going with the galvenized that I can get easily and maybe I can special order the same thing out of other materials after I have something made up and working.

I do get that SS would be ideal and having something custom made would be nicer. However, part of me feels a bit secure in having this made out of off the shelf pieces. While the SS may last forever, I have my doubts and think that I would be better off trying to look for a 1.5" elbow in a far off country than someone with a stocked supply of 316 stainless tubing and the skill to property fab a piece should there be a failure at some point.
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Old 09-04-2014, 18:10   #9
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Re: DIY Mixing elbow

Stainless (316) parts are just as "standard" as galvanized. A large supplier will carry both. They are commonly used and available. The stainless parts are just as easy to fab and weld as the galvanized. Both are weldable with stick, MIG, TIG, in other words any standard welding rig. The difference with the 316 is that it will last long after the galvanized has failed and left you stuck in a foreign port dealing with repairs.

I've built galvanized exhaust risers, they work well. But their service life is significantly shorter. I'd suggest you make your decision on cost versus service life. Standardness, fixability, etc of one versus the other is a non issue.
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Old 09-04-2014, 18:57   #10
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Re: DIY Mixing elbow

No doubt stainless is the way to go if you can afford it and it is available in your area .
The first one that I did with galvanize pipe I was anchored in Massacre Bay on the North coast of Haiti , I hitched a ride into Cape Haitian to the hardware store . Five years or so later I did it again in Antigua , stainless was available but it was Race Week and the wait would be longer that I wanted to stay .
Capt. Force was always more successful that me but only because he came up for parole before I did .
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Old 09-04-2014, 20:24   #11
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Re: DIY Mixing elbow

I just made two for my MD7A for about $130 in material and a few hours work. SS bits from Onlinemetals, good for small quantities of all kinds of material, metal and plastics.
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Old 14-04-2014, 15:21   #12
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Re: DIY Mixing elbow

Well, I finally managed to hobble something together. SS was not really readily available and I wanted to just get it done. So I got what I could in black iron and the rest in ganvalized, now that I have a working "model" so to speak I think I will follow some of the other advise here and build another out of SS parts that I can find online and since I have a working replacement in place there's no rush and will probably put together the SS one when I have time and keep in on board for when it's needed or whenever the next time I am taking apart that part of the motor.

Painted the whole thing with high temp engine paint afterwards as well.
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Old 14-04-2014, 16:33   #13
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Re: DIY Mixing elbow

You may want to wrap the riser part before the water injection with fiberglass tape if there is a chance of something touching it or being close to it - that part will get very hot.

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Old 14-04-2014, 16:58   #14
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Re: DIY Mixing elbow

I did something similar but with Bronze fittings. If you wrap the riser with fiberglass tape, think about smearing silicone caulking over the fiberglass tape. It keeps it from getting gross and you from getting fiberglass splinters. You might even get artsy.
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Old 14-04-2014, 18:52   #15
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Re: DIY Mixing elbow

Mine, SS.
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