- December 18, 2020 at 2:03 pm #13476
Tony Athens, a Cummins marine engine guru, has stated that exhaust system and aftercooler issues have killed more of these engines than all other causes combined. I thought what with it being winter, Covid, etc. now would be a good time to address some important items.
If your engine still has the “stock” white double jacketed exhaust elbow, you are on “borrowed time”. As Tony refers to these “doomed to fail” elbows (all exhaust elbows eventually fail, but if these fail you could be sending water into your turbo and even your engine) when they fail (and maybe before) they can cause very costly damage (maybe the need for a new engine). See the photo showing the white elbow for an example of these elbows with the poor setup. To remedy the problem, you will have to get a “custom” dry exhaust elbow made. We had ours made by Scott at National Marine Exhaust in Marysville, Wa., but there are other options like Tony at Seaboard Marine in Southern Cal. With the custom elbow, when it fails (10++ years), water cannot run uphill to get into the turbo avoiding the need for major repairs. Gravity can be a wonderful thing. 🙂 See photo of my current exhaust.
Aftercoolers require regular servicing or replacement before normally required. Properly serviced aftercoolers can operate for many years and thousands of hours (10,000 plus). A new aftercooler costs about $3400 US just for the part. Even a brand new one, unless purchased from Seaboard Marine, should be taken apart and “greased up” following Tony Athens’ protocol. The same protocol (shown under Tony’s Tips on his website sbmar.com) is used when conducting routine maintenance on these. The reason for this is the fact that you have several dissimilar metals in close contact all within an electolyte (salt water) with only a small “o” ring keeping the seawater out of your engine air intake. The grease helps to keep corrosion under control by providing a barrier between all of the various metals. The aftercooler core needs regular cleaning by being removed from the engine so both the air side and the water side can be adequately cleaned. Just flushing with products like “Barnacle Buster” do not do the complete job! While BB will help remove calcium buildup and clean the water passages, it does nothing for the air side nor the corrosion issues. The air side gets “gummed up” with an oily residue over time due to the CCV (Air Sep) system recycling oily air from the engine back into the air intake eventually “air starving” the engine if left long enough. Plus, as outlined in Tony’s protocols, the aftercooler should be pressure tested to ensure no leaks as an essential part of the regular servicing (we don’t want salt water entering our engines, right.). Tony has a complete video under Tony’s Tips on his website on how to service your aftercooler. I did my own, and it is not that hard to do. I figure I saved over $500 labour.
Disclaimer: I have no affiliation with Tony Athens, Seaboard Marine, or National Marine Exhaust. I am just a satisfied customer of each, and am thankful that Tony provides tons of free info on his site regarding marine engines (especially Cummins).December 18, 2020 at 2:13 pm #13477
Here are the photos from above post (I hope):
Pilitak NT 37-068December 18, 2020 at 2:28 pm #13478
Sorry for the multiple posts, these could have been combined. Under normal conditions, aftercoolers should be serviced by removing them from the engine for bench servicing (removal only takes about 15 minutes) and a complete “tear down” every 2-3 years. If you freshwater flush your engine regularly and store it over the winter that way (assuming you don’t just keep using it), you can increase the time frame to 3-4, maybe 5 years (according to what I saw from Tony’s info). Conditions can vary, and a conservative approach is best (monitoring both corrosion and “gunk” buildup on the air side) until you can determine what is best for your situation. Most mechanics if left to their own methods, do not adequately grease the aftercooler parts. Neither does Cummins. Monitor them, or at least ask them to follow the protocol. It only takes a couple of minutes longer to add the “extra” grease.
TomJanuary 18, 2021 at 9:01 am #13508CarmenParticipant
I recently purchased my NT32 with a 6BT (no after cooler) 220hp Cummins. The survey indicated pinhole leaks in the exhaust elbow and muffler and recommends replacing both. I have been reading several articles related to this and trying to decide how to proceed. My elbow turns down 45 degrees at the exit of the turbocharger. I need to remove it to inspect the impeller but I’m thinking I can replace like for like and not get into a vertical loop arrangement. I intend to ask Scott if he can take a look as they manufactured the elbow in place to see if they are doing anything different on an arrangement like mine. I did read an article on SENTOA about how spots after the elbow and inadequate water flow and mixing but I’m don’t think I have that going on.
I’m posting this to follow up on Toms maintenance post to ask if anyone with a 6BT has modified their exhaust configuration.
BobJanuary 18, 2021 at 9:02 am #13509CarmenParticipant
Here’s another viewpoint.January 20, 2021 at 2:29 pm #13511
Good idea asking Scott at National Marine for his opinion. I would also suggest posting photos with questions regarding your exhaust on Tony Athen’s website (sbmar.com) in the Cummins forum area. You will need in addition to the above photos, a photo showing where the water is injected into the white elbow. Due to your layout (batteries and water lift muffler being close by) it may be difficult to obtain a good photo, but do the best you can. If that set up is what I think it may be, you are not immune from potential problems, but not in as bad a position as the one shown in the earlier photo I posted (showing the setup in the early NT 37’s).
There are photos on Tony’s site under Tony’s Tips, showing what the inside (exhaust side) of your turbo should look like and what it will look like if it has been ingesting saltwater. Taking off the elbow will allow this inspection. If you are replacing the elbow anyway, best to get it “right” this time. Between Scott and Tony you will get it figured out.
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