Just got my third Yanmar 3YM30 exhaust elbow in 600 hours. Has anyone tried getting them ceramic coated. There seems to be a lot of shops offering this type of product or service. Makes sense to me but ??
exhaust elbows
- Thread starter nick8489
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If you're only getting 200 hrs/elbow .....................
............... you are probably deep sixing them because they are badly carboned up. I doubt there is too much corrosion at that age.
I've had moderate success cleaning the coke out of mine by using oven cleaner, and not some earth muffin, new age, earth friendly formula. Find the nastiest stuff available and leave the exhaust pass filled with it for two or three days.
Makes the scraping a little easier.
............... you are probably deep sixing them because they are badly carboned up. I doubt there is too much corrosion at that age.
I've had moderate success cleaning the coke out of mine by using oven cleaner, and not some earth muffin, new age, earth friendly formula. Find the nastiest stuff available and leave the exhaust pass filled with it for two or three days.
Makes the scraping a little easier.
Nick: You should be running that engine at 70-80% of the max rated RPM. I think your engine is rated at 3600 (not sure). That would dictate that you run it at 2700-3000 rpms while cruising.
You are doing something wrong in running your engine. (Probably running it too lightly as mentioned above.) I just replaced the 30 year old exhaust elbow on my Yanmar and I didn't really need to. Once it was off for inspection though, it was silly not to put a new one back on.
Check your prop pitch. Sounds like you may be overloading the engine. You should be able to turn max rated engine RPM with a clean bottom and prop in smooth current free water. Also, don't baby a diesel they like to be run at 70-80% cruise RPM.
Yanmar also recommends periodic short blasts of wide open throttle to clean it out. Lugging them by over propping or running at low RPM are just two of the issue that can lead to plugged elbows. Short engine runs are also not good as the engine never gets to full operating temperature.
Yanmar also recommends periodic short blasts of wide open throttle to clean it out. Lugging them by over propping or running at low RPM are just two of the issue that can lead to plugged elbows. Short engine runs are also not good as the engine never gets to full operating temperature.
One More Thought
We are all assuming that the elbow is coked up, which is the most likely scenario. But you didn't say what the problem is. Obviously there is a problem of some kind. I did mine last year, and it wasn't bad after years and hundreds of hours. Is the elbow coked up or corroded. If it's coked up the above advice is good. I use muratic acid and soak the elbow in that. This works good and is not damaging to the elbow. If it's corroded, although I have never heard of this, you probably have some wierd kind of electrolysis going on. More info. please.
We are all assuming that the elbow is coked up, which is the most likely scenario. But you didn't say what the problem is. Obviously there is a problem of some kind. I did mine last year, and it wasn't bad after years and hundreds of hours. Is the elbow coked up or corroded. If it's coked up the above advice is good. I use muratic acid and soak the elbow in that. This works good and is not damaging to the elbow. If it's corroded, although I have never heard of this, you probably have some wierd kind of electrolysis going on. More info. please.
Thanks for the replies but my question is about ceramic coatings. As H33 owners will know the exhaust elbow designon this installation is bad and many of us have this problem and it is difficult to get more than a couple of years out of them despite all the well intentioned running advice given on this thread!
Nick: I have never heard about anyone else complaining about this issue. What engine do you have on this boat.
Are your mixing elbows coking up or is there some other issue?
Are your mixing elbows coking up or is there some other issue?
I have the 2004 3YM30.
The H33 has a space limitation and Hunter got approval to fit what many mechanics consider an old, inadaquate design cast iron mixer which was fitted to the old smaller GM series engines. It colkes up very quickly. Most other production yachts using this engine have a superior stainless steel unit. I quote the first Yanmar mehanic who showed up with an unfittable elbow at 200 hours "jeez the've fiitted the wrong elbow mate" then a phone call the next day " No it's an approved installation, must have been approved by some dickhead"
Just so I don't get another avalanche of useless responses, I usually cruise at 2500 rpm, never idle for charging as have full solar panels and hammer it at 3000 plus rpm when coming home up the leads. I am not overpropped, have a feathering prop which has a varible pitch facility and can get full 3600 revs in gear on the run!!
My question remains has anyone experience with ceramic coating?
It costs around $100.
If it is coke then a ceramic coating won't do squat. iI it's corrosion it might slow it but not by much. Do you guys still have high sulfur diesel?
ceramic
Never heard of ceramic coating on a marine mixing elbow. Automotive and motorcycle exhaust yes, but not marine wet exhaust. I'm not even sure how they'd get a ceramic coating inside the water passages to stick. If you're on your 3rd elbow since 2004 there is a problem and it's not the elbows. Are you having an overheat issue? Keep in mind that some of the early 2004 H33's with the 3YM engine had a smaller capacity heat exchanger (looked the same, less tubes) that caused some people problems.
Not trying to be a jerk but I'd find another mechanic.
Never heard of ceramic coating on a marine mixing elbow. Automotive and motorcycle exhaust yes, but not marine wet exhaust. I'm not even sure how they'd get a ceramic coating inside the water passages to stick. If you're on your 3rd elbow since 2004 there is a problem and it's not the elbows. Are you having an overheat issue? Keep in mind that some of the early 2004 H33's with the 3YM engine had a smaller capacity heat exchanger (looked the same, less tubes) that caused some people problems.
Not trying to be a jerk but I'd find another mechanic.
Good question Main Sail you obviously are well informed!
I understand that there has been some improvement lately due to pressure from the automtive lobby as diesels cars are now in high demand but I don't have any quantitative info.
High Again Main Sail! I forgot to add that there is both corrosion due to salt water lying in the exit end of the elbow (another bad Hunter design as it is too cose to the water line) and coke build up. My homespun theory was that coke might have more difficulty sticking to a ceramic finish and that it would certainly help with the corrosion.
I have the new heat exchanger. I am not alone with this elbow life on an H33 it is definitely a poor design and I thihk specific to this boat. All I'm trying to do is improve the situation and perhaps get to 3 years instead of two! I have given the new elbow to a fabricator friend who is going to look at it with a view to designing a bespoke stainless one. Nice high rise , smooth interior, more gradual bend; could be the ducks nuts and worth another couple of horses!
If anyone here on the right side up part of the world (I see Nick is from OZ) is interested in having a S.S. elbow built, I know a fellow who builds and repairs things like custom exhaust components for the fishing fleet. I'll draw it up for him (no charge to SBO folks) but I would need photos, measurements, etc. If the Hunter's group could locate a boat in Maine I could look at, that would be ideal.
It would be an expensive elbow but might save money in the long run.
Nick,
The reason I suggest the problem isn't the elbow (or it's installation) is that here on the east coast US at least, we're not seeing these needing replacement at anywhere near the frequency you're experiencing. Even in charter fleets many of not most of the 2004/5 H33's are still operating fine with their original elbows. My gut reaction is you have something else going on. Any chance it could be something weird like the muffler installed backwards?
The reason I suggest the problem isn't the elbow (or it's installation) is that here on the east coast US at least, we're not seeing these needing replacement at anywhere near the frequency you're experiencing. Even in charter fleets many of not most of the 2004/5 H33's are still operating fine with their original elbows. My gut reaction is you have something else going on. Any chance it could be something weird like the muffler installed backwards?
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