Discussion in 'Engines' started by Fixinbones, Nov 12, 2019.
Well even replacing the aftercoolers every 6 years, overall maintenance is still cheaper than MANs
I don't know if I buy that anymore. I have been maintaining one MAN 1100 HP yacht since 2011. The motors have been **** good, we haven't had to touch anything internally on the engines in the 8 years I've been dealing with her. The oil is more expensive, yeah..... but it's a 400 hour change interval if you're doing a lot of hours per year. The filter prices aren't terrible, paying around $70 a fuel filter or oil filters...… We did the 1000 hour service once during my tenure with the yacht......
How much is the 1000 hour service?
Remember the johnson 70? 5500 hours on the 3412Es when sold. 4000 hours while I ran the boat in 8 years. All I did was one aftercooler cleaning, a flush of the HEs, one starter, one fuel cooler and clean the gear coolers once. The after cooler cleaning was part of a 3000 service which was like $4000 per engine.
So far in 3 1/2 years and 1600 hours on the C32s, besides the initial AC upgrade, we replaced one ECU, and did an acid flush.
I think the 1000 hour service was $16k. We have only done in once.
When you add the aftercooler replacement price to the C32's or C18's etc, then it gets costly. Especially if done every 6 years. Seems the 3412's didn't have aftercooler issues. I'm not really sure why CAT aftercoolers are only going 6 years or so. But I know of 3 rebuilds in 3 different boats because of aftercooler's leaking, 2 C18's and 1 C32.
Like Boulder GT3 said, 6 year replacement life for an aftercooler is short, I agree. Cat either has a bad design or using the wrong metal. Plus they recommend cleaning and testing every 2 years or 1000hrs, lot of $$$ every 6 years for one item.
What I learned on the 3126 ACs, the solder Cat uses (Specs) does not like any solders we could find for repairs to meld with it. New, old, many flux samples. Close but nothing repeatable.
Further, there is a fine line getting the Cat solder to flow (any) before material damage happens.
This original solder also does not like salt water as scores and pitting was observed at contact areas.
The Cat design is actually pretty good. The parts are sandwiched so well, there is really a minimal amount of solder exposed to salt water. But where there is, it will leak internally.
For a 110% fresh water boat, your ACs should last for ever.
I am convinced Cat does not want their ACs repaired.
I am convinced Cat is in the AC and HE business and it's fixed to sell more.
Don't buy a AC in 6 years, they are time-bombed.
Cat will sell you a new motor in 7 years.
Wanna spend some big bux on some ideas with little to no returns?
I just wish I had some time with a quality oven and lots of AC cores and learn how to take them apart with out damage. Then reassemble with serviceable solder.
Another idea was to acid wash out the water passages, mount in a machine like a rotor cast mold spinner while injecting an epoxy under air pressure. This would coat the water contact surfaces and seal any leaks.
I just finished the 1000hr on my MAN 1550's. It was about $17k and that included gear coolers and fixing a broken exhaust manifold bolt. I think I get a little break because the boat is pretty serviceable but the 1550's are the worst to do because they have two after coolers.
My point wasn't a MAN vs CAT thing though. CAT has best in class engineering, experience and capability, I just wonder why the AC's seem to be a weak point. Again, my C12's had 3 revisions and I think the predecessor 3196 had long running AC issues. The AC's just seem to be an ongoing issue.
In my opinion, it is quite unusual for an aftercooler to fail in such a short duration. If they are failing as a result of corrosion in the tubestack, either the material selection was not right or a fault in the design of the aftercooler or simply lack of galvanic protection. I have seen aftercoolers on other engine makes which have been running for 10 to 15 years with absolutely no issues.
Exactly, which is what everyone else is re-iterating. Man's have no galvanic protection (zincs) yet they last and last. I've seen many other engine aftercoolers last and last. I know of one QSM 11 boat with around 700 hours that's 14 years old and aftercoolers have never been touched.
MAN s do have galvanic protection but it’s a totally different and 100 % reliable system ....transom anodes .
This is tricky to get your head around .
MAN s used a large zinc fitted to the transom submerged in the salt solution/ sea .This is permanent connected to the engine by a large earth strap .
There 24 v system to run the engines ECUs , sensors, starter motor and other stuff is isolated from the boat .
When you switch off or run there’s always a anodic protection because of the seawater circuit .Thats why the coolers or any other part with a tendency for bimetallic corrosion does NOT corrode with MAN s .
With CAT ( and few others ) they approach bimetallic corrosion on a individual basis of each wet part , by fitting a localised pencil anode .
This means a manufacturer in theory can be a little lax with suppliers as third parties in the manufacturer of out sourced parts from a different anodic / catholic electrochemical difference .
This is because the fall back is the chunk of zinc screwed in .......but for the protection to actually work from a chemistry POV there needs to be a salt solution . A salt solution for the zinc to leach out its protection.
Trouble is bad design of the CAT coolers means they can in some circumstances drain out when the engines not running leaving the protection of the zinc literally hanging in the air .
That’s what’s happening .
Summary with CAT cooler corrosion .
wider range of electrochemically different metals in the coolers
Drying of the zincs .
MAN make everything in house on one site inc the coolers and so there electrochemical difference of components is tiny compared to CAT
There’s never loss of Zinc continuity with the transom submerged anode system .
Litigation wise CAT are covered with the 6 y throw away part regime.
The drying out thing is also a function of the installer....relative height of the WL and cooler height etc .....hence the roulette of why some CAT coolers do leak sooner than others and others seem to last the 6 year distance ....just !
see the two anodes 4 kgs of zinc for each engine , never dries out , permanently connected.
So the Two anodic protection regimes need to be handled differently.
With MAN you don’t need to fresh water flush indeed the higher concentration of the salt solution is beneficial allowing the protective parts of the Zinc to move about and ......protect .A fresh water flush may harm the general protection gained from the stern anodes .Choking the supply of protective chemistry .
With CAT ( + other localised zinc like you geny ? ) a fresh water flush may be beneficial if the thing drains out and the local zinc hangs in the air for weeks of inactivity. A weaker residual salt solution will slow down any bimetallic corrosion.
How ever if the bimetallic potentials are massive due to huge component difference ( out sourced loss of quality control to a 3 rd party ? ) then even if the zinc is wet , ie not drained out to dry then once past a certain point a weaker salt solution be beneficial.
Hope this helps ?
Thank you for the detailed explanation. I will add, that on plane the transom zincs are out of the water and not protecting, but that is for a short period of time compared to the life of the engine.
What I can't wrap my head around is many other manufacturers do use aftercoolers like Cat does and rely on zincs on the raw water parts of the engine. The old Detroits, Cummins QSM 11's and other models, MTUs I believe and various other manufacturers and they're not having aftercooler issues or even requiring the 6 year change. I did have an after cooler leak on a 2 year old/200 hour Series 60 (D.D.) one time but we caught it soon enough before any engine damage was done. Seems like CAT has been having a lot of aftercooler issues for decades now. 3116's and 3196s in the 90's had a lot of aftercooler issues even. Meanwhile some other models like the 3412's didn't.
The localised pencil anode system can work fine as you have experienced with other manufacturers and especially generators ......if the bimetallic ness for want of a better word is not great .Ie a close as possible as many components from a electrochemical pov .
Sufficient weight of zincs , changed on spec , and importantly they stay wet , even wet if there’s been a bit ot a lot of post shut down drain down .
I guess it would be interesting to see the relative weights of the coolers / heat exchangers and pencil anodes of each manufacturer and total weight of zinc bolted to the engines .To see where CAT are with this ?
Bottom line is minimising dissimilarity between metals in contact with sea water .Suspect historically CAT have had 3 rd party quality control issues due to sloppy outsourcing.
So the engineers back at HQ can design a theoretical great heat exchanger and perhaps test the first few .....all ok ......enter a contract .....then a revolving door of techs at HQ and the ball is dropped .Damage limitation comes next ....followed by loosing a huge class action law suit .Then a cover your arse statement along the lines “ replace every 6 years “ in the service manual .
In effect making them a throw away part .
Fiammetta42. I don't think it is the dissimilar metal issue. My thought is that Cat likes to put the aftercooler right smack dab on the top of the engine, up high. My thought is the heat from the engine cooling off after running and the height, cause the seawater to drain out of the aftercooler and possibly what salt is left crystallizes and gets super concentrated. On Cummins and Volvo's and others I see the aftercooler on the side of the engine and fairly low. But, I'm not an engineer, so this is just a guess.
Based on quotes I've had for Cat is close to Man when comparing the same service and then you add the 6 year ac replacement plus the 2year service. I had two boats with older Mans, the ac's and he's were cupronickel in good shape and original, also engines had isolated grounds that supposedly reduced galvanic problems.
Cat c12's/3196's were well known for there ac problems. A Cat mechanic said one of the main problems was the water pipes would expand and retract which could damaged the O-rings causing leaks. The ac sets directly over the valve intakes with no dams and water can be drawn into valves and cylinders.