The mixing elbow on my '98 H376 broke off from the manifold. My mechanic, whom I trust implicitly, attributes this to a design flaw. He says that the unsupported weight of the elbow coupled with the heat and vibration of the engine puts too much stress on the connection to the manifold. His solution is to have his welder fashion a new fitting. I'm not sure of the details as this is based on a preliminary phone conversation and I'm no mechanic. He did say that he could replace it as was done previously but that it would probably fail again in a few years. We were very fortunate that when this mishap occurred, we were returning from a longer weekend cruise and were only a few hundred yards from our marina entrance on a beautiful calm day. My fear is this reoccurring in the middle of the Chesapeake Bay in heavy weather. Has anyone else experienced this issue and, if so, what was your solution.
H376 Mixing Elbow
- Thread starter rkssail
- Start date
And that pretty well sums it up. The connector has corroded through.
I've inspected mine (on occasion) and replaced it twice in 24 years when it probably didn't need it.
As shown on my mixing elbow after an internal inspection, all the parts are heavy cast iron with the exception of that screwed connector between the two heavy parts. Yours is slightly different. The connectors we have are just thin pipe, the weakest part of the assembly. The connector is plain steel and corrodes more easily than the other two cast iron parts. You've got to keep an eye on its INTERNAL condition.
Have it replaced and make a note to have it inspected in 4 - 5 years. Make sure none of those hoses connected to your model are pulling on the assembly.
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I had a similar experience. The threaded coupler broke as we were prepping to leave the dock. I noticed a change in tone of the exhaust and went below, smelt the exhaust and saw the water spewing out the manifold so shut the engine down.
I was able to easily remove the coupler from the manifold, so I ordered a new stainless elbow and coupler for significantly less than OEM Yanmar parts. It took less time to remove the broken parts and install the new parts than it did to clean up the mess made when the coupler broke, maybe 10 minutes total for the removal and replacement.
BTW my original coupler lasted 32 years.
I was able to easily remove the coupler from the manifold, so I ordered a new stainless elbow and coupler for significantly less than OEM Yanmar parts. It took less time to remove the broken parts and install the new parts than it did to clean up the mess made when the coupler broke, maybe 10 minutes total for the removal and replacement.
BTW my original coupler lasted 32 years.
You are blessed indeed. I've seen a number of complaints of failed couplers over the years on this site but I've got to say, I probably could have left the couplers in due to moderate corrosion but opted out for a new one.
Like you, my last mixing elbow was a SS one from HDI with a SS coupler. I've had it for 4 years so I'd better get around to checking it. I don't know how your got yours off so easily but mine requires the right arm of God to remove it after 4 - 5 years in service.
Replace with an SS HDI Elbow. And run the engine wide open periodically.
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Ditto on HDI! beautifully made SS parts for significantly less than yanmar cast iron. Escape's changed 7 years ago and still looks brand new
As far as a design flaw, my Yanmar 2GM20F is going on 36 years old….and as far as I know, the elbow has never been replaced (I am in fresh water).
As others have said, the connector is the weak point, and the mixing elbow is prone to getting plugged up with rust…so it need to be replaced periodically.
Greg
As others have said, the connector is the weak point, and the mixing elbow is prone to getting plugged up with rust…so it need to be replaced periodically.
Greg
Yes, to a minor extent. Nothing serious. Nothing to be alarmed about. The engine still ran well at this point :
How these engines manage to run never ceases to amaze me. IMO, the mixing elbow is the most important thing on the engine to be watched as it can do the most damage to the engine. On an equal par to running with no oil pressure.
The greatest fear of all is having the overhead wall that separates the hot gasses from the incoming sea water, perforate. Should this happen, one runs the danger of having sea water enter the exhaust manifold when the engine is SHUT DOWN. When this happens the next thing the sea water will look for is a partially open exhaust valve, and once it gets through there, it's all over. That's all she wrote, folks.
Below is another elbow I hacked open to give a better view of the internals in a less corroded condition :
The carbon deposits are harder than steel although I did once manage to remove most of the deposits from this item by leaving the mixing elbow submerged in "Easy Off" oven cleaner for six months. Unfortunately, the corrosion was so severe, particularly the dam where the hot gasses entered, it was put on display in my shelves of old boat parts labelled "never to be used." Went HDI SS after this event.
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So what is the proper maintenance on an elbow? Is it run time related or just age? I imagine a properly running engine is a must.
Don't run the engine at idle or low speeds for long periods of time. Charging batteries by idling the engine without a load is a major cause of carbon build up.
Run at 80% of WOT when cruising.
Frequently run the engine at WOT for 15 minutes or so often to heat the carbon up and burn it off.
Remove and inspect the elbow every so often, depending on how the engine has been operated. Lots of low speed operation, inspect and clean more often.
I open mine up every 4 - 5 years. I now have 4 years coming up on my HDI elbow and coupling which I will pull apart to see what's going on in there. SS can be funny stuff and fail where you are positive it should be working. Accelerated loss of the chromium oxide prophylactic coating is the most common cause of SS failure.
Definitely. But I have a properly running engine from brand new, run at 80%, and don't idle to charge the batteries and still get what you see in post #10. That was around ten years old. No justice at all sometimes
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