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Old 22-11-2021, 17:17   #1
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Yanmar Exhaust - Bristol 32

Boat:
32' Bristol Sloop 1981, Yanmar 3YM30 30hp diesel, Water Injection exhaust. 2" x 2.5' exhaust down to existing 22 year old Allcraft SS 7"dia x 7" wet muffler (? gals) self underneath the engine (leaking after 22 years) to a side inlet. Discharge 2"x12' is up and over the top of the engine to the transom {see image below). Port side loop for injection pipe. Engine and exhaust hoses new in 2013. Engine compartment restricted. I don't know much about these systems.

Options:
1. Repair weld existing SS316 wet muffler, but it is old. Allcraft not found.
2. New Centek replacement in Vernalift 6"x6" or 8"x8" size. Fiberglass.
3. New Vetus Waterlift Plastic melts at 158 degrees F max continuous.
4. Shorten exhaust route by relocating wet muffler aft and below the shaft (in the keel) and route exhaust pipes around shaft. Requires disconnection of shaft and difficult pipe routing. Is this worthwhile to reduce pipe length from 12' to maybe 7'? Of course this will make working on the very short shaft, cutlass and stuffing box much harder in an already restricted space.

Comments:
I have a hard time getting used to Fiberglass or Plastic for the hot muffler gases, even if cooled by water.
I have read about engine inundation in following seas and would like to prevent it. Would like to improve engine performance and reduce back pressure and reduce noise, if it is possible. I have read several threads about this Perkins replacement wet muffler, Locate vetus wet muffler, Yanmar Exhaust Muffler Help

Goal:
Looking for experience and advice regarding this installation routing and replacement mufflers. Should I go for the biggest Vernalift muffler that will fit and simply install it in the current location? What about double chamber mufflers?

Muffler Alternatives.
2”x 2” Vernalift Side In 6”x9” SKU:1500264 0.43 gallons
2”x 2” Vernalift™ Side In 6” X 9” SKU: 1500054 0.43 gallons
2 x 2” Vernalift Side angle in 6”x9” SKU:1500268 0.43 gallons
2” X 2” Vernalift™ (Side In) 8” X 8 SKU 1500026 0.78 gallons
Dual Stage
2” X 2” Vernalift™ Dual Stage 8” X 12” Top Out SKU 1529001 1.06 gallons
2” X 2” Vernalift™ Dual Stage 8” X 11.25” SKU 1520200 0.87 gallons

Also Vetus Plastic
Vetus Dual Stage Waterlock NLP50 6.5” dia x 10” high 1.2 gallons 2” hose
Vetus Waterlock NLPH50 4.3” dia x 25.75” overall .8 gallons 2” hose
They make a black or white version that is heavier duty and higher temp rating. NLPxx(S) Gray 158 ̊F NLPxx(S)HD Black 482 ̊F
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Old 23-11-2021, 07:26   #2
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Re: Yanmar Exhaust - Bristol 32

Centek has a page showing different exhaust systems Centek_Vernalift_Install_Guidelines

I believe the 3ym30 comes with an exhaust elbow and fitting for the vacuum break and water introduction to the exhaust system (for cooling) See this pdf page which states "There are two types of mixing elbows, the L-type and the U-type. The mixing elbow is attached to the exhaust manifold."
I have to check the engine to see if it is U-type. See https://www.sailmagazine.com/diy/mai...esel-exhaustSo we likely have the U-type connection since it is a sailboat and the engine is partially below the waterline. These types of connections can get clogged and should be checked on a regular basis see the forums on this. The vacuum break should be checked on a regular basis and I think I am going to try to move it from outboard towards the centerline in the port locker, just below the deck.

Some 3YM30 specs:
  • Exhaust Pipe Outer Diameter Connection 2"
  • Min. Eng. Room Fresh Air Exchanges 194.23 cu ft/min
  • Max. Back Pressure (within 9.8" of manifold inlet) 1500 mmAq 14.7 kPa (0.15 kgf/cm2)
  • Max. Exhaust Temperature (within 9.8" of manifold inlet) 600C(1112F)
  • Maximum EngineRoom Ambient Temperature 60C (140F)
A temperature gun would be useful. How is back pressure tested?

This thread on 25' Yanmar 3GM30 Exhaust Run (!)... Max Length / Height ? is somewhat reassuring but it is not the same engine. Post 19 "all the water in the hose will run back and fill the waterlock." so the wet muffler should be sized to hold water = 12' exhaust hose x 2" dia . And it should be a little larger.
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Old 23-11-2021, 08:24   #3
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Re: Yanmar Exhaust - Bristol 32

Maintaining your wet exhaust system
1. Check the vacuum breaker operation regularly. (spriing)
2. Check the exhaust riser elbow and back pressure --How? What are the symptoms of a clogged exhaust riser?
3. Make sure following seas won't enter the exhaust system.

The end of Sail's Maintain your Diesel Exhaust has an excellent description for replacement of the elbow and explains how the system should work.
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Old 23-11-2021, 09:29   #4
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Re: Yanmar Exhaust - Bristol 32

Josh Glidden, Centek Design Engineer responded promptly to some questions:


Quote:
Hi Rick,

It sounds like you are on the right track with considering the volume. Generally speaking we recommend to use the largest volume muffler you can fit into the space. Normally with a 2 system, a 12x12 lift muffler is more than sufficient. The extra volume helps reduce noise and backflow risks.

To address your heat concerns, if your mixing tank or manifold is mixing the water and exhaust gas properly you should have no issue with using our FRP products. We use a high temp resin, specially designed for this exact purpose.

The dual stage mufflers are great but need to be installed above the waterline. Based on what you have told me about your routing, I assume the muffler will be below the waterline. If that is not the case, the dual stage mufflers are fantastic.

I have attached some literature for your reference. Please do not hesitate to reach out to me with more questions or concerns.

Best,

Josh Glidden
Product Design Engineer

Since the wet muffler is below the waterline, I can't use a dual stage which would reduce noise.
I hope I have enough room for a 12x12, we will see.
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Old 23-11-2021, 10:04   #5
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Re: Yanmar Exhaust - Bristol 32

Some thoughts having gone down this road a few times. Reducing back pressure and eliminating water egress into your engine are the 2 most important goals.

Yanmar's U shaped cast iron mixing elbows are IMO a poor design from a back pressure point of view and they corrode easily. Your outlet hole on the exhaust manifold has the ID of 1.5" pipe. The LH/RH coupling is also 1.5" BSP pipe. However, the 2" outlet on the mixing elbow is deceiving. Its interior is threaded for 1.25" pipe and this is AFTER the water is injected. This is a constriction that must be removed. Use 1.5" 316L ss pipe to form an upside-down U and inject your cooling water on the downside of the U which precludes injection water from getting into your manifold. Then use a barbed fitting to adapt to 2" ID exhaust hose.

From your diagram, it appears that the exhaust is exiting fairly high up the transom. I would suggest fabricating or buying a gooseneck fitting and exiting lower on the transom. This helps eliminate water ingress in a following sea.

Centek's advice is solid. Use the largest waterlock that will fit.
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Old 23-11-2021, 10:25   #6
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Re: Yanmar Exhaust - Bristol 32

Thanks Kenbo. That is very helpful. The engine is 8 yrs old about 750 hours. How would I check for build up and back pressure values?

Also to replace this I will as you suggest,
Quote:
"Use 1.5" 316L ss pipe to form an upside-down U and inject your cooling water on the downside of the U which precludes injection water from getting into your manifold. Then use a barbed fitting to adapt to 2" ID exhaust hose."
How would I make up the injection of cooling water and doesn't that require a proper fititing downward so raw water does not go the wrong way?

Maybe someone makes these better designed SS316L riser elbows?
I am going to check out the transom outlet, I may have shown it wrong, but I don't think there is an elbow there.
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Old 23-11-2021, 10:42   #7
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Re: Yanmar Exhaust - Bristol 32

On those Yanmar engines with the cast iron exhaust elbow (not the mixing elbow), I drill and tap a 1/8" npt thread and use a 5 PSI gauge. It'll pulsate with the engine but it's readable. If you find it pulsates too much to read you can add a needle valve to choke the pulsations. 1500mmAq is a bit more than 2 PSIG. Insert a 1/8" npt plug when you're done.

I'm not sure what you mean by "check for blockage". But typically CI corrodes where the cooling water is injected.

Something like this https://www.asap-supplies.com/produc...m-hose-2187351 would suit your injection on the downside needs.

And keep in mind that Yanmar uses BSP threads not NPT so buy your nipples and fittings accordingly.
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Old 23-11-2021, 10:51   #8
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Re: Yanmar Exhaust - Bristol 32

Kenbo you are a wealth of knowledge. Thank you.
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Old 23-11-2021, 11:53   #9
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Re: Yanmar Exhaust - Bristol 32

1.5" 316L ss BSP thread

Found this BSP = British Standard Pipe Thread, not tapered.
Is Class 150 medium pressure cast 316L ss ok?
Does the Yanmar exhaust use BSP threads?
Can I use a 90 degree Street Elbow? (Not the right thread) for one of the elbows or should I use a short 316L ss nipple?

I am finding 316ss elbows with NPT thread which is National Pipe Tapered, NPS is straight thread, but probably not right. Looks like it might be a special order in the US.

I find Pipe Dream Fittings in England has the right fittings

Granger does have Elbow: 316 Stainless Steel, 1 1/2 in x 1 1/2 in Fitting Pipe Size, Female BSPP x Female BSPP for $50 so two of those with a short 316L nipple would work ok?

Then add the British Seaflow Multi-Choice Exhaust Outlet Spray Head (1.5" BSPM / 51mm Hose) Part No: 2187351 158 british lb.

And then dril and tap 1/8" tap npt the elbow to test for pressure with 1/8" plug.

McMaster Carr has BMP fittings but they are not big enough.
https://www.mcmaster.com/stainless-s...tyle~threaded/



What pipe dope?
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Old 23-11-2021, 12:46   #10
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Re: Yanmar Exhaust - Bristol 32

-Having the muffler low and as large as possible is a good thing, but it only needs big enough to contain what water is in the exhaust hose aft of it.
-A vented loop wont necessarily stop water ingress through the large exhaust hose. It can slowly work it's way into your aft cylinder from wind waves right through the muffler without some system of stopping it.
-I like a high loop in the hose just prior to exiting the hull because it avoids gradual ingress from following waves or wind waves at a dock. (I got water in a Perkins from simply sitting at a dock overnight.) That boat had a huge waterlift muffler.
-Fiberglass mufflers work fine with the heat. If you cant find the perfect one you can add an outlet/inlet where you need it if you can do glass work. I made an entire custom muffler once for a gen set.
A 2" exhaust hose 10 ft long holds 1.6 gallons of water if full. Exhaust hoses are not near full from engine exhaust water.

If redoing it all you could consider this: (?)
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Old 23-11-2021, 13:30   #11
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Re: Yanmar Exhaust - Bristol 32

Quote:
Originally Posted by rgleason View Post
1.5" 316L ss BSP thread

Found this BSP = British Standard Pipe Thread, not tapered.
Is Class 150 medium pressure cast 316L ss ok?
Does the Yanmar exhaust use BSP threads?
Can I use a 90 degree Street Elbow? (Not the right thread) for one of the elbows or should I use a short 316L ss nipple?

I am finding 316ss elbows with NPT thread which is National Pipe Tapered, NPS is straight thread, but probably not right. Looks like it might be a special order in the US.

I find Pipe Dream Fittings in England has the right fittings

Granger does have Elbow: 316 Stainless Steel, 1 1/2 in x 1 1/2 in Fitting Pipe Size, Female BSPP x Female BSPP for $50 so two of those with a short 316L nipple would work ok?

Then add the British Seaflow Multi-Choice Exhaust Outlet Spray Head (1.5" BSPM / 51mm Hose) Part No: 2187351 158 british lb.

And then dril and tap 1/8" tap npt the elbow to test for pressure with 1/8" plug.

McMaster Carr has BMP fittings but they are not big enough.
https://www.mcmaster.com/stainless-s...tyle~threaded/



What pipe dope?
BSP threaded fittings are very common in the UK. Spend some time on ASAP Supplies website https://www.asap-supplies.com/. They have everything you need to do the job and the posted prices include VAT so your price will be 20% less. All the fittings and nipples should be BSP tapered not parallel.

Yes, you can use a street 90. And Cheechako's advice to use a high 180 bend and exit out the transom lower is great advice. You can use something like this to fashion the transom exit piping https://www.asap-supplies.com/produc...52mm-c-1200333. But you possibly can find that cheaper in the US.
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Old 23-11-2021, 20:38   #12
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Re: Yanmar Exhaust - Bristol 32

Cheechako and Kenbo, thank you!
The turned up solution with 180 degree elbow looks good. I did find Centek C-1200333 180 elbow 2" for $117
and I think I will get these 2" Elbows 423007 & 423047 SS316L fittings and the other items from ASAP as I won't need them immediately.

Josh from Centek wrote back again and here is his suggestion for muffler
Quote:
The volume is dictated by the routing, most importantly. Assume the routing between the engine and muffler & muffler and high point after outlet will run back into the muffler. Less than 1/2 of the hose volume will be water. So if you have 10’ of 2” DIA hose that will flow into the muffler at shut down: 120” * PI * r^2 =377 in^3 = 1.63gal-1.63gal * (1/2) = 0.82 gal. My recommendation would be to use a 2” in x 2” out lift muffler such as 1500027.

Looking at the routing in the Cruiser’s thread: It is definitely not ideal. In a perfect world, we would like the exhaust to go vertical after the muffler (<5’) then run downhill to the hull penetration. Running diagonally for an extended length will add back pressure and can potentially cause the engine run inefficiently. That being said, I am guessing that this routing configuration was how the previous exhaust system was set up so we know that it is possible.
The routing shown is where the previous exhaust went. I will look into an alternative route in upper part of the port locker, but fitting bulky sails through the hatch may become a problem with the hose in the way.

Defender has Centek Vernalift 1500027 for Side In-Top Out Wet Exhaust Muffler (1500027) Inlet/Outlet Diameter: 2", Muffler: 10.04" Diameter x 10.16" H 1.31 gallons for about $240


I have to check to see if there is adequate clearance under the engine and may have to lower the support shelf.


I will look into the possibility of improving the route.

Thank you all!
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Old 23-11-2021, 21:18   #13
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Re: Yanmar Exhaust - Bristol 32

+ 1 for Kenbos suggestions.
I was an ss welder but would always go for a f/glass or plastic muffler as you just need a temp alarm.
Neither was i impressed with the yanmar cast-iron mixing elbow design, it's responsible for the deaths of more YS series Yanmars than any other single factor IME as a parts seller for them.
I made up my own mixing elbow minus the design flaw out of sched 10 316L stick welded. Any ss fabricator could make one easy enough. Of course the drawback is the elbow is hot but ceramic wrap takes care of that problem, It doesnt seem to be clogging like Yanmars either.
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Old 23-11-2021, 23:46   #14
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Re: Yanmar Exhaust - Bristol 32

I put a centex on my last boat.. great product. New boat has a vetus and so far no complaints. Good luck!

Greg
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Old 24-11-2021, 10:48   #15
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Re: Yanmar Exhaust - Bristol 32

Quote:
Originally Posted by rgleason View Post
Cheechako and Kenbo, thank you!
The turned up solution with 180 degree elbow looks good.
Josh from Centek wrote back again and here is his suggestion for muffler
The routing shown is where the previous exhaust went. I will look into an alternative route in upper part of the port locker, but fitting bulky sails through the hatch may become a problem with the hose in the way.

Defender has Centek Vernalift 1500027 for Side In-Top Out Wet Exhaust Muffler (1500027) Inlet/Outlet Diameter: 2", Muffler: 10.04" Diameter x 10.16" H 1.31 gallons for about $240


I have to check to see if there is adequate clearance under the engine and may have to lower the support shelf.


I will look into the possibility of improving the route.

Thank you all!
If you are talking about elbows to make the 180 degree loop turn, just bend the hose if you have room. The wire wound exhaust hose will bend into maybe a...12-16" wide loop... less clamps, less flow obstructions...
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