Our boat has only sailed in clean fresh water. Do we have to be concerned with cleaning the mixing elbow? Is this where the water that has cooled the engine goes out into the exhaust? How does one tell if it is time to clean or replace it?
yanmar mixing elbow
- Thread starter carl1553
- Start date
- Status
Yes
Even freshwater will rust up the aprerture, which is compounded by the exhaust building up inside. It's a remarkable small space to run both exhaust and water through, and it clogs within 3-5 years depending. If you run the engine at the sweet spot RPM instead of slowly, and if you run it hard at least once 2 hours a month, you might get 10 years out of an elbow. Problem is, you don't know if the previous owner did both. Symptoms include dying out, water no longer coming out the exhaust, eventually won't turn over. All of these are bad because in the attempt to troubleshoot, you're inadvertently filling the muffler with water, which can backflow into the cylinders which is very too bad. Suggest consulting the yard or closest Yanmar dealer. It's not that big a deal to replace, as long as you do it by dismantling the elbow at the manifold, which has four bolts attached to the engine. (You can't get the elbow off any other way due to leverage issues. Be sure to buy a new gasket for the manifold.) If the elbow is okay, put it back and call it PM. If not, don't even think of cleaning it, simply replace for $150. Either way, you'll motor along and sleep easy.
Even freshwater will rust up the aprerture, which is compounded by the exhaust building up inside. It's a remarkable small space to run both exhaust and water through, and it clogs within 3-5 years depending. If you run the engine at the sweet spot RPM instead of slowly, and if you run it hard at least once 2 hours a month, you might get 10 years out of an elbow. Problem is, you don't know if the previous owner did both. Symptoms include dying out, water no longer coming out the exhaust, eventually won't turn over. All of these are bad because in the attempt to troubleshoot, you're inadvertently filling the muffler with water, which can backflow into the cylinders which is very too bad. Suggest consulting the yard or closest Yanmar dealer. It's not that big a deal to replace, as long as you do it by dismantling the elbow at the manifold, which has four bolts attached to the engine. (You can't get the elbow off any other way due to leverage issues. Be sure to buy a new gasket for the manifold.) If the elbow is okay, put it back and call it PM. If not, don't even think of cleaning it, simply replace for $150. Either way, you'll motor along and sleep easy.
Elbow issues
Besides corrosion the biggest issue with mixing elbows is carbon accumulation which will eventually choke off the passage inside the elbow. This will occur in fresh or salt water. This is aggravated with a high percentage of low load/low RPM usage. When I removed ours last month and took it to our local Yanmar dealer they recommended not cleaning it (no corrosion but some carbon build-up) but replacing it at 3 year intervals (assuming regular usage.) I think that is an overly short schedule but since it was only $122 I figured it was a reasonable maintenance expediture. You could wait until you see symptoms from the engine (reduced power and RPM potential, excessive black smoke) but since an overly restricted elbow could introduce salt water into your engine or fail from unseen corrosion on the inside and introduce water and exhaust into the boat I'd suggest at least pulling it for inspection is prudent. I'd suggest no more than 5 years if you use your boat regularly.
Besides corrosion the biggest issue with mixing elbows is carbon accumulation which will eventually choke off the passage inside the elbow. This will occur in fresh or salt water. This is aggravated with a high percentage of low load/low RPM usage. When I removed ours last month and took it to our local Yanmar dealer they recommended not cleaning it (no corrosion but some carbon build-up) but replacing it at 3 year intervals (assuming regular usage.) I think that is an overly short schedule but since it was only $122 I figured it was a reasonable maintenance expediture. You could wait until you see symptoms from the engine (reduced power and RPM potential, excessive black smoke) but since an overly restricted elbow could introduce salt water into your engine or fail from unseen corrosion on the inside and introduce water and exhaust into the boat I'd suggest at least pulling it for inspection is prudent. I'd suggest no more than 5 years if you use your boat regularly.
When we check ours it was fine!
Nancy: We checked our after several years and it was fine. If you run your engine as the proper RPM and you are in fresh water you will probably get 7-10 years before this is an issue. Of course it never hurts to check. I actually removed mine because I had purchased a new one already. I gave it to a friend at the marina and he is using it.
Nancy: We checked our after several years and it was fine. If you run your engine as the proper RPM and you are in fresh water you will probably get 7-10 years before this is an issue. Of course it never hurts to check. I actually removed mine because I had purchased a new one already. I gave it to a friend at the marina and he is using it.
I got tired of Yanmar and their marketing
tactics. This is a perrenial problem which comes up all the time and has caused me more trouble and expense than anything else on board. I made a replacement from black iron pipe from Home Depot for about $20. It is fine after two years but I carry a spare set of parts. Check the archives if you want more info. FYI: don't let your engine run a long time at slow speeds or the clogging of the elbow will happen sooner that way.
tactics. This is a perrenial problem which comes up all the time and has caused me more trouble and expense than anything else on board. I made a replacement from black iron pipe from Home Depot for about $20. It is fine after two years but I carry a spare set of parts. Check the archives if you want more info. FYI: don't let your engine run a long time at slow speeds or the clogging of the elbow will happen sooner that way.
Mixing Elbow replacement
Our own experience... After reading all these posts on mixing elbow (this subject comes back very often), I got worried, ordered the parts and change our's last fall. After 14 years in fresh water (6 months a year), it was like new inside and out after inspection. No rust or build up anywhere. Since I had purchased the new one and the coupler, I changed it anyway. I think this will vary a lot depending on water type and owner RPM habits.
Our own experience... After reading all these posts on mixing elbow (this subject comes back very often), I got worried, ordered the parts and change our's last fall. After 14 years in fresh water (6 months a year), it was like new inside and out after inspection. No rust or build up anywhere. Since I had purchased the new one and the coupler, I changed it anyway. I think this will vary a lot depending on water type and owner RPM habits.
DO NOT CLEAN
Nancy During a Yanmar maintanence course, we were warned not to clean mixing elbows. The separating wall between the gas and water is very thin. If cleaned, micro holes can permit water to enter the exhaust valves resulting in a hydraulic lock! They recommend replacing roughly every 5 years
Nancy During a Yanmar maintanence course, we were warned not to clean mixing elbows. The separating wall between the gas and water is very thin. If cleaned, micro holes can permit water to enter the exhaust valves resulting in a hydraulic lock! They recommend replacing roughly every 5 years
Franklin is right
I say clean it. It should last a long time in fresh water - a lot more than five years. Yanmar is making a lot of money on elbows. It is a bad design if you ask me. I made mine out of black pipe for $20.
I say clean it. It should last a long time in fresh water - a lot more than five years. Yanmar is making a lot of money on elbows. It is a bad design if you ask me. I made mine out of black pipe for $20.
Mixing Elbow Cleaning
Everyone makes a big deal of this! You do need to be a bit of a contortionist to reach in from the front of the engine and pry off the exhaust hose with screw drivers and WD-40. Once that's done remove the four bolts that bolt the assembly onto the exhaust manifold. Take the whole thing to an automotive garage and ask them to use their bench vise and a large wrench to disassemble the elbow from the left hand/right hand threaded coupling and that coupling from the 'U' shaped injection elbow. At that point you should be able to tell if you want to chissel or power wire brush the carbon out or just replace the worst pieces. The flanged elbow from the manifold won't typicall need replacing; the right& left threaded coupling is thin stainless steel and can be damaged in a vise; the 'U' shaped casting is cast iron with two parallel chambers built in. the smaller chamber has a screw-in brass nipple for the water injection hose. The larger chamber will be where you find rock hard carbon build-up. Put it back together with nonsieze on the threads and a new gasket onto the manifold. Run you engine at 80% of max RPM and you'l get many years out of your efforts.
Everyone makes a big deal of this! You do need to be a bit of a contortionist to reach in from the front of the engine and pry off the exhaust hose with screw drivers and WD-40. Once that's done remove the four bolts that bolt the assembly onto the exhaust manifold. Take the whole thing to an automotive garage and ask them to use their bench vise and a large wrench to disassemble the elbow from the left hand/right hand threaded coupling and that coupling from the 'U' shaped injection elbow. At that point you should be able to tell if you want to chissel or power wire brush the carbon out or just replace the worst pieces. The flanged elbow from the manifold won't typicall need replacing; the right& left threaded coupling is thin stainless steel and can be damaged in a vise; the 'U' shaped casting is cast iron with two parallel chambers built in. the smaller chamber has a screw-in brass nipple for the water injection hose. The larger chamber will be where you find rock hard carbon build-up. Put it back together with nonsieze on the threads and a new gasket onto the manifold. Run you engine at 80% of max RPM and you'l get many years out of your efforts.
Had mine replaced 2 years ago
It was amazing to see how clogged up it was .. Mine had at least 10 years on it.
It was amazing to see how clogged up it was .. Mine had at least 10 years on it.
Add Water Temp Gauge
Like many 2GM20F owners I experienced mixing elbow problems. I decided to add a water temp gauge and now I can detect temperature increases. A couple of years ago I noticed a 10-degree gradual increase, pulled the elbow and confirmed it was severely clogged again. My advice is to add temp gauge and detect the problem before alarm rings. If anyone is interested contact me through Owners Directory and I can supply pictures/instructions showing my installation of water temp and oil pressure gauges.
Like many 2GM20F owners I experienced mixing elbow problems. I decided to add a water temp gauge and now I can detect temperature increases. A couple of years ago I noticed a 10-degree gradual increase, pulled the elbow and confirmed it was severely clogged again. My advice is to add temp gauge and detect the problem before alarm rings. If anyone is interested contact me through Owners Directory and I can supply pictures/instructions showing my installation of water temp and oil pressure gauges.
- Status