6CTA Starboard Aftercooler Recommendation

[Harold]

Good morning SBA team, 

I pulled the starboard aftercooler for maintenance and discovered some corrosion. I have a pair of 2002 6CTA 450’s which were last serviced in 2019 and installed fresh water strainer caps at the same time. I was surprised at the amount of salt build up, I religiously flush the engines after every use except when cruising multiple days which is only  about 10-12 days a year. There was quite the buildup in the hose exiting the fuel cooler into the gear cooler. That hose is bent a bit making that angle and that’s where the buildup was. I am planning to remove the fuel cooler and moving the gear cooler to that area. 

After soaking the housing with penetrating oil for a few days I couldn’t get it to budge so I had a machine shop press the core for me. It didn’t take much pressure but here is what was discovered.

I block sanded the bottom surface for awhile and took off a considerable amount of material. I sanded the top end to clean it up a bit. There are still some pitted areas around the bottom seal area and there’s  a pronounced groove on the top surface. I stopped there to get some professional opinions on what can be saved.

As for the core, the pictures say it all. There was quite a bit of corrosion on the bottom of the core and I’m not sure if that’s salvageable or worth pressure testing/reusing. I haven’t gotten to the port side yet but I’m expecting it will be just as bad.

Need any more detail? What do you guys recommend? 

 

Topic

[Harold]

Results of Taste Test

I finally got around to putting it all back together. I bypassed the fuel cooler and remounted the aftercooler. I started a fresh water flush as I normally do with the sea cock open.  After ~10 minutes I shut it down and pulled the lower zinc and did my taste test. It definitely was salty water as I expected, not pure salt water but still a bit salty. Based on this experience I will now start closing the sea cock during the flush. We have great water pressure at the dock which I always check before hooking up to flush. I’ll start close cock flushing per the instructions in the video and be sure to open it BEFORE shutting down the engine. That should help me stay out of trouble and hopefully reduce the buildup in the core tubes. I’ll do another taste test after that and maybe again after every ten flushes or so to stay on top of it. 

Thanks to the SM team for the assistance and guidance!

[Tony Athens]

SPECIFICALLY ?? —-Not quite true at all    If you are going to quote me, let’s read it all ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~   https://www.sbmar.com/articles/the-benefits-of-fresh-water-flushing-your-marine-diesel-engine/ IF the water flow from the dock is greater than the needs of the engine at an idle (which it usually is if a good valve / water flow / pressure is at the dock and you have a good hose and 5/8 or bigger plumbing all the way to the T in your system) the engine will only have fresh water in it after a couple of minutes of idling. Shut off the engine first and the fresh water will just go out the bottom of the boat because the seacock is STILL open. Since fresh water is lighter than seawater, even after months with the seacock left open, you´ll find fresh water still in the system… So, you still want to close your seacock? Maybe you just can’t handle not knowing the exact mixture of fresh and saltwater going into the engine. Maybe the dock hose doesn’t supply tons of water and you really want to know you’ve flushed it out thoroughly. Whatever the reason, you want to close it and flush with 100% fresh water only.

[Richard Dodson]

In Tony’s tips he specifically mentions no need to close the seacock.  I leave mine open and after flushing I’m removing the flush cap, it’s obvious that the strainer is filled with fresh water. I use the outlet in the ER with the boat hooked up to shore water. 

[Gerasimos]

I could be wrong but I thought that if you leave the seacock open you end up sucking in raw water even with your hose supplying fresh, so its not a true fresh water flush its probably still mostly salt water. 

[Harold]

Pressure Test Update

After sanding I took the aftercooler core and case to the radiator shop. I requested they pressure test the core first then reassemble it using plenty of lube and pressure test the complete unit. They called and let me know it passed the tests and it’s ready for pickup. The plan is to remove the fuel cooler then put it all back together next week. After that I’ll replace the flush hose, fire it up and give it the taste test (by removing the lower zinc). After that it’s on to the port side.  

[Harold]

The flush time is always around ten minutes per side. That may be the issue, not long enough? I never close the sea strainer cock during the flush. I didn’t think I needed to. The pressure at the dock is respectable and for sure is fresh water. I have not been back to the boat yet to investigate it further, I will be there next week. I plan to remove the flush cap to get a good look at the flush valve to be sure it’s functioning correctly. One suspicion I have is the hose running from the cockpit hatch to the flush valve. It’s an ordinary garden hose which may be  collapsing during the flush. I plan to replace it with reinforced hose and keep an eye on it. I’ll let you know what I find. 

[Harold]

Continued Sanding

I got back into town and continued with the block sanding. Here Are pictures of the progress. I took off a considerable amount on each end, not sure if it was a credit card’s worth, maybe more. I did have considerable dust. I’m looking for opinions on the progress. Keep going or am I there?   I’m taking the core to have it pressure tested. If all goes well I will assemble the core in the housing and have the entire unit pressure tested. I will post results when I get the core back.  As always I appreciate your time. 

[Richard Dodson]

Just curious, how long are you running the engines with the fresh water hooked up and are you leaving the seacock open or closed?

[Tony Athens]

I 100% agree with Rob–Something is not adding up and I suspect it’s related the the “service” in 2019 ( actually the lack of) or you are not really flushing it with 100% fresh water..

 

Continue to block sand–

 

As to the core– Needs to be pressure tested by itself after a through cleaning with 10% HCL/water acid on the tube side, and solvent cleaning on the fin side.

 

 

[Rob Schepis]

Your approach sounds reasonable.  But you do need to figure out why the seawater side looks so bad if you were freshwater flushing since the last service.  Check that your flush setup and how you are using it is doing what it is intended to do.  

[Harold]

It had a full service in 2019 but unfortunately I didn’t do it. I took it to reputable radiator shop in San Diego so I never saw what it looked like internally at that time. The boat was new to me and I had my plate full servicing the heat exchangers, impellers, replacing  the starter, full time job, etc. I regret not attempting the service myself. 

As for the strainer flush, I ran a hose to each strainer back to the opening of the hatch in the cockpit so I could easily flush them without climbing down to the bilge. I have not been back to the boat yet to disconnect and inspect the hoses to see if there is any blockage or issues there. What was really surprising was the salt crust build  up in the silicone hose at the bottom of the fuel cooler. I will definitely spend some time checking it out and giving it the taste test. Shame on me for not tasting it from the beginning…  

I don’t think I took  a credit card’s worth of thickness off the bottom housing surface, close to it but not quite. I’ll try some finer grit paper and see what I end up with. As for the top surface not much was removed. I’ll work on it to see if I can get the groove out without removing too much. 

As for the core, that’s what scares me the most. If you guys think it’s salvageable I will take it for a pressure test and repair estimate. I’m not that experienced in knowing by just looking at it so if you think it is I’ll have it tested. 

I’m out of town until next week so I won’t be able to post my progress until then. In the mean time here are the steps I am considering:  

1. Continue block sanding the housing and post new pictures for comment
2. Pressure test the core and review findings and repair estimates 
3. Based on the sanding and pressure testing, if all looks good then assemble the unit following the SB lubing, greasing standard and pressure test the entire unit. 
4. Consider purchasing new SMX after coolers for a more sound piece of mind??

Let me know what you guys think. 

 

 

[Rob Schepis]

Are you saying the aftercooler had a full bench service and greasing in 2019 and has been fresh water flushed ever since?  Something is not adding up.  Did you verify the discharge is not salty when you installed your flush setup?

The core looks like it got a little beat up. It needs a thorough inspection, cleaning and then a pressure test before assembly.

You can take just about a credit card thickness off the housing ends.  Will that get you where you need to be?

[Author]

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