Flush Raw Water System

[dhays]

The previous owner and I did just that, and three years after I bought the boat, I had a hose burst just downstream of the raw water pump. A BB flush put all kinds of coloration in the bucket. Maybe FW flushing helped, but it certainly did not eliminate it. I will be flushing at least every two years.

Good input. thanks.

 

[dhays]

Keep in mind, fresh water will cause a coating to form on zinc anodes, essentially rendering them inert. The coating can be cleaned off using a ScotchBrite pad, however that requires removal of pencil anodes, at which point you might simply chose to replace it unless it's like new. Hull anodes can of course be cleaned by a diver. Until cleaned their effectiveness will be diminished. Alternatively, you can use aluminum anodes, whcih are immune to this phenomenon.



More on the subject here https://stevedmarineconsulting.com/galvanic-isolators-and-zinc-anode-selection/

Yeah, I did switch to aluminum pencil anodes for the engine now that I’m during a fresh water flush every time I get back to the dock.

 

[captaindah]

Rydlyme

Use Rydlyme. Works well on engine (raw and heat exchanger) as well as A/C and water heater. Also takes rust stains off fiberglass. Great chemical, but difficult to find in gallon containers.

 

[rgano]

Keep in mind, fresh water will cause a coating to form on zinc anodes, essentially rendering them inert. The coating can be cleaned off using a ScotchBrite pad, however that requires removal of pencil anodes, at which point you might simply chose to replace it unless it's like new. Hull anodes can of course be cleaned by a diver. Until cleaned their effectiveness will be diminished. Alternatively, you can use aluminum anodes, whcih are immune to this phenomenon.

More on the subject here https://stevedmarineconsulting.com/galvanic-isolators-and-zinc-anode-selection/

I religiously freshwater rinse my Yanmar 6LPA after every run but never did with my Ford-Lehman 120s. With zinc anodes in both boats there was always a gooey brownish coating collecting on the zincs (checked every 90 days or less on both boats). I cleaned it off and either changed or just reinstalled the anodes depending upon condition. IRT the Yanmar, since it sits long periods with freshwater in contact with the anodes and relatively brief periods underway in salt, I figured it should be treated as a freshwater boat and switched to Secure Core AL anoded. Same brownish goo collects except on the fuel cooler and intercooler zinc which being high on the engine are not immersed in water once the engine is stopped and rarely need changing. To be candid, I am not sure whether the zinc anodes protecting the system during running in salt or the AL anoded protecting during non-operating periods are better for the engine. One wonders if the dry-during-idleness anodes should not be zinc and the rest AL.

 

[Southern Boater]

Freshwater flushing (as often as possible - after every use is "best") will delay the need for removing all saltwater based cooling items for servicing. If you have an aftercooler, it should be serviced every 2-3 years (off the engine) if you don't FW flush. This off the engine servicing entails: removal of fuel cooler, gear oil cooler, aftercooler, and heat exchanger; acid cleaning of the saltwater side; pressure testing; proper reassembly of the items (especially the aftercooler - new O rings, everything well greased to reduce future corrosion); reinstallation of the previous items; and new coolant.
Just running BB through will not ensure that "all is well" for the long term. All of these items can be subject to "failure" where leaking can occur possibly resulting in raw water in your transmission, or raw water in the coolant, or raw water in the air side of your engine. Pressure testing should find problems before they can cause "real issues". Also, the air side of the aftercooler is not touched at all by the BB solution, and it needs cleaned as well or your engine can become "air starved".

Not saying that BB (or flushing with other products) is a bad idea, just trying to "look at the whole picture".
Tom

You have raised some very valid points Tom, there is no substitute for a strip down and pressure testing.

 

[Steve DAntonio]

The only drawback I have found to the aluminum anodes is the pencil version does expand a bit, making it difficult to remove. Where that happens I have instructed owners to stay with zinc if in salt water. Since the engine and hull are essentially in 'different bodies of water', there is no issue with mixing anodes types. While not recommended, if you do mix Al and Zn in the same body of water it's not harmful per se, with the result being that the Al tends to protect the Zn, and when the Al is gone, the Zn is then consumed.

 

[sunchaser]

For after coolers, removal, manual cleaning and pressure testing is preferred. Why? A year or two in a marine engine rebuild shop will provide plenty of examples as blocked up air side and /or perils of water entering engine due to leaky ACs or bad exhaust elbows.

BB may be cheaper in the short run for your water side of the AC, but periodic removal is advisable in the long run. Especially to get the air side clean.

 

[firehoser75]

For after coolers, removal, manual cleaning and pressure testing is preferred. Why? A year or two in a marine engine rebuild shop will provide plenty of examples as blocked up air side and /or perils of water entering engine due to leaky ACs or bad exhaust elbows.

BB may be cheaper in the short run for your water side of the AC, but periodic removal is advisable in the long run. Especially to get the air side clean.

One more reason. If you don't control the corrosion that will develop between the various metals used in the construction of most aftercoolers, you will be replacing it WAY sooner than would otherwise be necessary. These are expensive items!! When badly corroded, the insert bundle (core) maybe next to impossible to remove (or badly damaged by removal), with the O ring sealing surfaces becoming badly pitted and therefore unable to seal out the salt water! Just using an "acid like" flush will not prevent this nor will it clean the "air side" of the aftercooler.

As far as I can see, there is no way to avoid (unless you just want to buy new aftercooler(s)) a proper "off engine" servicing every 2- 4 years if you want your aftercooler to perform properly and to last. Have a look at sbmar.com and search for "aftercooler" and you will see what I mean.

 

[Comodave]

The only drawback I have found to the aluminum anodes is the pencil version does expand a bit, making it difficult to remove. Where that happens I have instructed owners to stay with zinc if in salt water. Since the engine and hull are essentially in 'different bodies of water', there is no issue with mixing anodes types. While not recommended, if you do mix Al and Zn in the same body of water it's not harmful per se, with the result being that the Al tends to protect the Zn, and when the Al is gone, the Zn is then consumed.

Last year we had no problem getting the old aluminum anode out of the heat exchanger but this year we saw what you said, the anode seemed to swell up a bit and wouldn’t come out. We had to pull the end cap off and push it out from the inside. Not a big deal but I was wondering what had happened. Thanks for the info, now ai understand why it did that.

 

[catalinajack]

I got tired of dealing with swelled anodes (zinc and aluminum) in my exchangers. I simply changed to 3/8 inch anodes rather than using 1/2 inchers. Problem solved although they need to be changed more often. I'm okay with that given the trade-off.

 

[Steve DAntonio]

Last year we had no problem getting the old aluminum anode out of the heat exchanger but this year we saw what you said, the anode seemed to swell up a bit and wouldn’t come out. We had to pull the end cap off and push it out from the inside. Not a big deal but I was wondering what had happened. Thanks for the info, now ai understand why it did that.

I see that as well, in some cases no swelling, in others it occurs. The more active the anode, the more it will generate aluminum hydroxide "fluff", or swell. It means it's working as intended.

I'd recommend heat exchanger end cap removal every 2-3 years in any event. When I remove these I almost always find debris, including dead pencil anodes, trapped in this space, and impeding water flow.