Cleaning Yanmar 2GM20F Mixing Elbow

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Steve Dion

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Dec 2, 1999
15,184
Hunter Vision-36 Rio Vista, CA.
salt water and hot gases

I believe Pat has the explanation why he does not see coking of the exhaust elbow. The difference is the salt water. When the hot exhaust gases mix with the salt water it causes the coking. Now some of our neuclear rocket scientist should have the chemical breakdown.
 
RichH

RichH

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Feb 14, 2005
4,773
Tayana 37 cutter; I20/M20 SCOWS Worton Creek, MD
Its simple ....

When saltwater is heated above approx. 143 degrees F. the carbonates become insoluble and 'drop out' of the solution. Whats formed is primarily calcium carbonate - the basic building blocks of rocks. The earth 'makes' rocks in the same way. Ditto fresh water but since the dissolved carbonates in fresh water is less the rock-making is slower. How to remove the carbonates: use an inorganic acid such as muriatic/hydrochloric (but acids will also dissolve the metal) OR use a commercial boiler 'de-scaling' compound such as Marsolve or Rydlyme - they dont dissolve the metal, just the 'rocks'. The same stuff is used to de-scale/'pickle' fouled engines, exhaust manifold internals and fouled heat exchangers. BTW these commercial boiler de-scalers can be dumped down the drain as they quickly break down in the environment. If the exhaust manifold discharges into a 'tail piece' that 'points down at about 20 degrees, then its OEM and its cast iron. If the engine has a retrofit 'heat riser pipe' (constructed of black iron threaded pipe and discharging 'upwards') then its usally an aluminum injection elbow at the top of the heat riser 'loop'. Yanmar dealers offer both.
 
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patrick

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Jun 7, 2004
944
Birch Bay Washington
Hodgey, mine is insulated because

it is made from black iron fittings and does not have a water jacket on the top to cool it off. It is insulated to contain the heat. My theory is that it will not clog up if it is kept hot enough. It runs noticeably better with this exhaust than it ever did with the stock elbow. Note: My old stock elbow was cast iron and it was the inverted "U" type. It cracked after two mechanical cleanings and 5 years of use. My opinion is that the stock part is designed to fail. The price for a replacement was quoted to me as anywhere from $2xx to $4xx and it made no sense to me. I can replace the whole thing now for under $20 with parts I can get anywhere and the engine runs better to boot.
 
RichH

RichH

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Feb 14, 2005
4,773
Tayana 37 cutter; I20/M20 SCOWS Worton Creek, MD
Forgot to add .....

If you have old decomposed or aged diesel fuel (older than 6-12 months) in your tank where the lighter 'fractions' have volitized out through the tank vent and the 'heavier' fractions have begun to 'agglomerate' into particles and gums, these gums dont burn very well in the combustion chamber and will 'blow through' the engine and will 'drop out' in the region of the water injection elbow (along with the carbonates). So, if you are getting continual blockage of 'coke' at that point of the injection elbow it also may mean that you have old dead fuel. Diesel fuel's shelf life is only 6 -12 months until it starts to go 'bad'; the warmer the tank oil the shorter the shelf-life.
 
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Neil Hodgson

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Nov 24, 2005
46
Hunter 29.5 Merritt Island, H 29.5, Miss Faith
Patrick..............

Good Man...... have you thought of patenting the design?
 
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patrick

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Jun 7, 2004
944
Birch Bay Washington
Hodgey, if it could be patented now,

I am sure Yanmar would have done so. They would have charged $500 for the parts which cost them $2 to make. Then they would prohibit the sale of them by dealers who are online or just not in the customers area. They would have to be assembled with special tools (pipe wrenches) which are very expensive (also patented) and only available to their dealers, too. I am not sure that they would be as successful at getting them to clog and fail as they have been with their stock part, though. What a racket!! Ralph, you can do this too. Get a 1 1/2 inch street ell. Screw it into the exhaust outlet on the manifold. Screw a close nipple into that and the center part of a tee onto that. On the down side of the tee, screw a 6 - 8 inch nipple to attach to the big exhaust hose. For the top of the tee, you have to find a double tapped 1 1/2 inch to 1/2 inch reducing bushing. That is the hardest part of this project - finding that part. Home Depot won't have one and will not even have a clue what you are asking for. Go to a plumbing place that knows. On the bottom part of the plug affix a 6 inch long by 1/2 inch pipe with the other end plugged and a series of 1/8 +/- inch holes drilled all around near the plugged end. I think I drilled about 12 holes in all directions from the center to the lower (plugged) end. On the top of the bushing, get an adapter to fit your cooling water hose which used to go to the old fitting on the old elbow. Attach that adapter to the 1/2 inch upper opening, clamp the hoses in place and you are done. Caution: Use lots of hi temp antisieze compound on all of the connections. On the big 1 1/2 inch joints - do NOT overtighten them. Do NOT use teflon tape. It makes a noxious possibly toxic (lethal) gas when heated too hot. Tighten the 1/2 inch pipes really well so they do not come apart from vibration. I used all black pipe but galvanized might work as well. I wrapped mine with fiberglass tape to protect my hands and things around it from the heat. Please report back when you have done this as to how well it works. I promise not to tell Yanmar. P.S. If you spend more than $20 US, you have not shopped well enough and need to go back to shopping school. Of course in Canada, taxes may push you over budget so that will be a challenge, too.
 
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Steve Dion

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Dec 2, 1999
15,184
Hunter Vision-36 Rio Vista, CA.
I did not pay $100 for the elbow

Patrick: I did not pay $100 for the new elbow, gasket
 
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patrick

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Jun 7, 2004
944
Birch Bay Washington
Steve, you can help me shop for

my next boat! :) The best price I got was $234 or something like that and another $35 for the one end reverse threaded adapter nipple thingy. Plus 8.5 percent tax. That was after calling suppliers for half a day and being told that they could not sell it to me cause I wasn't in their "area"! You should get a gold star for your shopping prowess. There is no such thing on the emoticon list. Maybe we should complain to Phil??? "I just hope this unit of yours does not blow out and gas you with CO some day, but you did save $100." That is just what my old Yanmar part did! It cracked and leaked exhaust into the cabin. Two years before that it just plugged up and stopped the engine from running so I could not get home for a week.
 
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patrick

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Jun 7, 2004
944
Birch Bay Washington
Yeah, but read further and you come to this:

Yanmar Territory Info: We sell sailing products to more than 75 countries around the globe and look forward to serving you. Yanmar products however, carry territory restrictions and we currently are only able to sell Yanmar products to the following locations: (NOTE: Yanmar engine sales are currently restricted to the West Michigan area) Bermuda Connecticut Deleware Illinois Indiana Iowa Maine Maryland Massachusetts Michigan Minnesota New Hampshire New Jersey New York North Carolina Ohio Pennsylvania Rhode Island South Carolina Vermont Virginia West Virginia Wisconsin If you have questions about this policy, email store_admin@torresen.com.
 
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