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This forum contains 5,838 Topics, 27,445 Replies, and 16,998 Contributing Members.
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- Cummins Marine Forum Topics
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Zinc or Aluminum Pencil Anodes in Fresh Water?
This topic has 3 replies, has 2 voices, and was last updated by
3 hours ago December 17, 2025 at 11:06 pm I boat in fresh water (Cummins 6CTA8.3-M3 engines) and all of the boat’s underwater anodes are Aluminum. However, all of the pencil anodes in the heat exchangers, aftercoolers, etc. are Zinc. I just pulled out the Zinc anodes from 2 years ago, and they are still almost at 100% (they just have a light coating on them). Should I be replacing them with Aluminum anodes? And if so, do I continue to use the brass anode-holders/plugs? (See photo of 2-y…
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in: Cummins Marine Engines
3 RepliesDecember 18, 2025 at 2:52 pm Check your gear cooler, there’s a few variants out there. Rob "Luck is the residue of good design."Last Post by:
posted: 3 hours ago
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Which Sherwood pump is this?
This topic has 0 replies, has 1 voices, and was last updated by 7 hours ago
December 18, 2025 at 11:25 am I had an overheat event this summer where an idler pulley fell apart and things started overheating. I was lucky that i shut it down within 3 seconds of the alarm going off and the engine only say maybe 210-220 degrees pulley’s have since been repaired sbmar style. based on the photo of our pump it clearly has been leaking recently. We think it may be related to the overheat- and may have leaked in short duration. Would you rebuild, replace, et…
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in: Cummins Marine Engines
0 Replies - Can you Help? ...be the First to Respond!
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Aftercooler Fins: Copper or Aluminum??
This topic has 6 replies, has 3 voices, and was last updated by
7 hours ago
December 16, 2025 at 2:20 am Hi Folks! I just finished cleaning this Aftercooler core from a 6CTA8.3-M3 engine (Built Date: 2000; CPL 2172). I assumed that the fins are made out of copper, and after soaking it with Brake Cleaner, I soaked the core overnight in Simple Green HD (purple stuff) with seemingly good results. However, I just Googled the Aftercooler part number (Cummins 3897630) and it says that it’s an “aluminum finned mid-vintage” core!! My concern is that if the…
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6 RepliesDecember 18, 2025 at 11:06 am Thanks Rob! I have a question about cleaning the heat exchangers. I cleaned the water side (rodded out the tubes, and filled them with 10:1 muriatic acid for 15 minutes). Do you bother doing any cleaning of the coolant-side (the coolant side looks pretty clean)? Thanks.Last Post by:
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Fuel Cooler needed in PNW?
This topic has 2 replies, has 2 voices, and was last updated by
1 day ago
October 20, 2025 at 4:18 pm I recently purchased a 2000 Nordic Tug 42′ with a QSM-11 dry exhaust. All the coolers haven’t been serviced in over 6 years, so I’m looking at dealing with that issue. I intend the boat to run only in PNW waters and north to BC & Alaska – so wondering I could /should remove the fuel cooler? I’d eliminate one cooler to be cleaned up, and reduce future points of failure. I’m wondering if anyone in this area has do…
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in: Cummins Marine Engines
2 RepliesDecember 17, 2025 at 6:29 pm Hi – are you Richard Cook who was with AMHS (Kennicott) ? If yes, you know me – Rich PrestonLast Post by:
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Cummins QSC Turbo Leak/Broken Bolt
This topic has 1 reply, has 1 voices, and was last updated by
1 day ago
December 12, 2025 at 11:47 am Hey All, First post here but I am looking for some help. Some background, I have a Cummins QSC with ~2400hrs and it in good shape, runs well, and is to date on all cooler maintenance, etc. Recently I was doing some other work in the bilge and noticed, when looking up at the backside of the turbo, what looked like an oil leak. It didn’t really make sense to me as it was on the Turbine side of the turbo not the compressor side. From t…
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in: Cummins Marine Engines
1 ReplyDecember 17, 2025 at 12:02 pm I’m hoping that these pictures work, I’ve been having trouble uploading images.Last Post by:
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4BT with Hurth overhaul. Stumped
This topic has 3 replies, has 2 voices, and was last updated by
1 day ago
December 12, 2025 at 10:35 am I am looking for some guidance on an Albin 27 SC I am working on. She has a 4BT CPL 741 and is paired to a Hurth HSW 630 A1. I am trying to figure out 4 issues: light amounts of white smoke, slight knocking sound that gets worse with RPM increase (I suspect fuel knock), engine goes past 180F when cruising over 1600-1700 RPM, and transmission spins when in gear with the engine OFF. The first 3 issues might be related. When I bought the …
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in: Cummins Marine Engines
3 RepliesDecember 17, 2025 at 6:59 am Thank you! I figured that was the case with the transmission, but the tow guy made me doubt myself. Fuel is clean, but I will check the lines to make sure they aren’t gummed up anywhere. Is there a way to check the fuel and airflow on this engine? I work on cars (enthusiast, not pro), so usually for me it’s as simple as hooking up my computer and running diagnostics and gathering live data. The boat is currently wint…Last Post by:
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Shaft Coupling Roll Pin remove problems?
This topic has 5 replies, has 2 voices, and was last updated by
3 days ago
December 9, 2025 at 10:12 pm Shaft Coupling Roll PIN remove problems? Engine 6BT; Gear MG-506; Shaft 1-3/4″ I want to remove the MG-506 Gear to Shaft Coupling. Trying a “Dry Run” with the boat in the water. Getting the 1/2″ Roll Pin with 5/16″ hole aka Split Pin out is the 1st step Split Coupling – Flange Diameter 5-3/4″; 6ea 5/8″,15/16″ HexHead Bolts with Nuts – a 3-7/8″ X 1/2″ Roll-Pin with a 5/16R…
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in: General Discussion
5 RepliesDecember 15, 2025 at 3:19 am The pin MOVED !! Using Hydraulic Ram. Revisions were made to the “one legged table” i.e a collar/ saddle was attached to prevent the ram from walking. The move was limited to ~ 3/4″ as the chain was over the pin on the underside. Hopefully when the boat is out of the water placing the chain alongside / aft of the pin it will be pushed all the way out. Thank you Tony for the suggestion of using Allen heads for pressing Pins In…Last Post by:
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QSC8.3500IDI CUMMINS
This topic has 1 reply, has 2 voices, and was last updated by
4 days ago December 14, 2025 at 8:47 am Looking for some input on possible issues with a 12 year old NEW QSC8.3500IDI Engine that has never been commissioned. I know there will be no factory warranty available because of its age just looking for some feedback, Engine has been installed always stored inside boat never finished. Thanks Sevino
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in: Cummins Marine Engines
1 ReplyDecember 14, 2025 at 12:58 pm Located where? Ambient temp will be about what with to attempt to start it? 1————service the entre seawater side– The impeller with need to be replaced.. The aftercooler–on the bench in pieces and serviced per my protocols 2———–Pre-lube ( 100% fresh oil & filter ) the engine and bar it over a few times. You need to “see” some oil flow under the valve cover.. Use low …Last Post by:
posted: 4 days ago
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2005 QSM11 661hp risk of dropping valves
This topic has 4 replies, has 3 voices, and was last updated by
4 days ago November 17, 2025 at 2:10 pm I am looking at a boat with a single 2005 QSM11, 10.8 Litre (661 cid) TA with 1,500 hrs. What is the likelihood this has the improper cam bearing installation? And if indeed what Tony suspected was true (blocked oil flow to valve gear leading to rapid rocker-arm pad wear), what could/should be done to mitigate future problems? Anything else I should be aware of with this engine? Thanks much in advance.
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in: Cummins Marine Engines
4 RepliesDecember 14, 2025 at 9:38 am What boat is this engine in and how is it used? Single engine trawler run low and slow or is it a Downeast where it is run harder than the trawler? Understanding what type of boat that it is in and how it is used and then the resulting fuel burn chart for that setup will be important for any kind of opinion beyond what is in the article in the previous response. Steve Lewis 2007 Kadey Krogen 44 WidebodyLast Post by:
posted: 4 days ago
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SMX air filter (S&B)
This topic has 1 reply, has 2 voices, and was last updated by
4 days ago December 14, 2025 at 4:55 am Sorry if this has previously been asked and answer but I could not find the info on the ad or forum. When using the SMX air filter for the first time do you need to add the red S&B oil? my filter is already red… but not sure if it’s pre oiled? also I live in Australia, I can’t get the S&B oil or kit here. Is there an equivalent… say something in the K&N range? thanks in advance.
Started by:
in: General Discussion
1 ReplyDecember 14, 2025 at 9:05 am It’s already pre-oiled Seaboard Founder & PresidentLast Post by:
posted: 4 days ago
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Aftercooler questions?
This topic has 2 replies, has 3 voices, and was last updated by
5 days ago December 13, 2025 at 2:22 am Hey everyone, Few quick questions. 1) how does everyone like to clean their Aftercooler cores? Anyone ever give them a soak in a nice diluted muriatic acid and water bath? 2) my Aftercoolers “twin engines” are dripping oil out from the bottom. Where the condensation relief valves are. I’ve been told to just stick a catch can there. I thought only water (condensation) is supposed drip from there? Is this my clear indication to clean my cores? lit…
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in: General Discussion
2 RepliesDecember 13, 2025 at 10:20 am Diluted “HCL or Pool acid” can only on the tubes/end brass plates.. Not on the copper fins.. Seaboard Founder & PresidentLast Post by:
posted: 5 days ago
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6bta re-wire diagram help
This topic has 0 replies, has 1 voices, and was last updated by 6 days ago
December 12, 2025 at 2:08 am Dear all, Long story short, I’m rewiring my panel and engine harness to both update instruments, and remove janky previous owner engine harness which very nearly torched the boat… Am keen that my work doesn’t torch the boat in the future. Have done wiring work before, motorcycles, my sailboat etc… but never on something that cost the family so much money 😉 I’ve followed a lot of the guides here (THANKS!) and I think…
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in: Cummins Marine Engines
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6bta possible fuel problems
This topic has 1 reply, has 2 voices, and was last updated by
1 week ago December 9, 2025 at 6:08 pm My 6bta 370 diamond series with 1300 hours suddenly will not open up past 2600 and is hesitant when throttling up it has a 5 or 6 second delay then she will turn up but still rpms fluctuating about 50 rpms like she wants to go but feels sluggish any idea where to look already changed all filters. Everything else seems ok aftercooler serviced. Also I have noticed a new sound coming from my exhaust almost like a hollow sound it’s just starte…
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in: Cummins Marine Engines
1 ReplyDecember 10, 2025 at 6:57 am Have you read through this? Understanding Low Power Troubleshooting Rob "Luck is the residue of good design."Last Post by:
posted: 1 week ago
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SMX Impeller – What they look like after 3 years
This topic has 3 replies, has 4 voices, and was last updated by
1 week ago
July 14, 2025 at 7:46 pm This is probably not all that important, but, since I had a picture of the impellor I just replaced I thought I’d post it here. I usually go 2 years on impellers so I don’t have to go chasing pieces, but, life happened and I spaced it out last year. The one pictured has 3 years, about 200 hours. I boat in the Mississippi River (Pool 26, just above St. Louis). We have quite a bit of mud in the water and also sand. SMX 17…
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in: General Discussion
3 RepliesDecember 9, 2025 at 4:43 pm When we bought our current boat I looked at the maintenance log and figured the PO just forgot to enter the last impeller change. The last entry showed 900 hrs and almost 6 years. I asked him and he said that was probably right because he changed that at 300 and it looked new so he figured it could go a long time. Yikes! I changed it (SMX) and it actually looked pretty good but had some cracks developing. Amazing.Last Post by:
posted: 1 week ago
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zf220a – shift lever repair
This topic has 2 replies, has 2 voices, and was last updated by
1 week ago December 7, 2025 at 4:18 pm My starboard zf220a shift lever froze up. I pulled the drift pin and shift lever. The internal snap ring, washers and detent ball all have rust on them. I sprayed it down with BP blaster and am letting it soak. I hope this does the trick. Just in case, they remain difficult to remove, does anyone have any tips for getting the stuck parts out? I have a repair kit I bought here ready for install. Thanks Bill
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in: Marine Transmissions
2 RepliesDecember 8, 2025 at 5:02 pm put a 3/16″ pin punch thru the hole and wedge out the valve shaft– be very aggressive–slide bar puller if needed –Use PB rust blaster as needed Seaboard Founder & PresidentLast Post by:
posted: 1 week ago
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Failing Lift Pump?
This topic has 2 replies, has 2 voices, and was last updated by
1 week ago
December 7, 2025 at 5:50 pm I have 6cta in my motor yacht. After running for any length of time when the starboard engine gets to heat sinked the idle drops from 630 to 580 in idle and as low as 530 in gear. The port motor does not have this issue. Could this be a failing lift pump?
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in: Cummins Marine Engines
2 RepliesDecember 8, 2025 at 8:50 am Serial number. 45990344 6CTA8.3-M3Last Post by:
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Do I need my shafts trued fit and faced?
This topic has 4 replies, has 3 voices, and was last updated by
1 week ago
November 22, 2025 at 12:27 pm I removed my couplers to replace my dripless seals. I’ve read online that I should remove the shafts as well and bring both the shafts and couplers to a prop shop for truing and alignment. Is this really necessary? I have reverse tapered couplings.
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in: General Discussion
4 RepliesDecember 7, 2025 at 5:35 pm Since the motors are already out, it’s a great opportunity to check cutlass bearings and motor mounts, and maybe propeller too.Last Post by:
posted: 1 week ago
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Fuel return manifold leak
This topic has 7 replies, has 2 voices, and was last updated by
1 week ago December 5, 2025 at 11:17 am I have a 99 6bta with a cracked return manifold. Does anyone know where a can find a new one. Or is there any other line that I can modify to fit? The port engine has a hard line from all injectors and over to the pump. The starboard engine has a hard line up until it crosses over where it becomes a flexible stainless line to the pump. The part number believe I need is 4019962. This looks like the one with the flexible end. I believe the port s…
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in: Cummins Marine Engines
7 RepliesDecember 7, 2025 at 4:58 pm You are right–no where to be had——————Only if I remove one from a new RECON.. A clever fabricator / combo hyd shop could come up with something to fix yours Seaboard Founder & PresidentLast Post by:
posted: 1 week ago
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Factory Wet Exhaust Elbow – Am I at Risk?
This topic has 12 replies, has 3 voices, and was last updated by
November 24, 2025 at 3:37 pm I am a new owner of a 2001 Sea Ray 400 Sedan Bridge, with Cummins 6CTA8.3-M3 (450 Diamond) engines (the boat has been in fresh water its entire life’s). The Factory Wet Exhaust Elbow “spill over” point is only a couple of inches above the water line which based on what I’ve read on this site is not a good thing! However, I am wondering if the Lift Muffler mitigates the risks? The lift muffler has 2 exits; a smaller exit going to the side of the …
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12 RepliesDecember 5, 2025 at 6:52 pm Your picture is a very accurate representation! The C/L of the Turbo is about 2” above the LWL, and the bottom of the “dip-tube elbow” coming out of the Lift-Muffler is about 1.75” above the C/L of the Turbo. I still have the Cummins Wet-Exhaust Elbows, but will be replacing them with the SMX Exhaust Elbow Mixers. (I believe in one of your articles, I read that for the system to be inherently safe, the bottom of the dip-tube elbow coming out of…Last Post by:
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2001 Cummins 6BTA – Mainship 390
This topic has 7 replies, has 5 voices, and was last updated by
1 week ago
November 26, 2025 at 6:32 pm Regarding ongoing issues with our 6BTA Cummins engine. We are currently in Georgetown, SC, and I want to provide a full summary so you have a clear understanding of why we need a Cummins specialist. The engine is a 2001 5.9 BTA with approximately 1,900 hours. The problems began about three weeks ago during our trip down the ICW to Florida. Timeline of Events • While idling for over 2.5 hours in Norfolk, followed by another 2 hours behind slow-mo…
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in: Cummins Marine Engines
7 RepliesDecember 5, 2025 at 7:00 am Pics don’t help. Need pics of entire setup. Like Tony said…..NO CLOSE UPSLast Post by:
posted: 1 week ago
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Zinc or Aluminum Pencil Anodes in Fresh Water?
