Cooling system flush: Marine age or hours?

[Dougcole]

Hey all,


Last year I built a recirculating cooling system flush system following the advice of some on this board. I used barnacle buster, it worked great.


How often do y'all flush your motors with it? Do you do it based on hours or just on a regular schedule?


The more often the better?


Thanks.

 

[DavidM]

More often is definitely not better. BB and others are corrosive and even though the metals in the raw water system are pretty corrosion resistant, you are losing some metal each time you acid flush.

On the boats I have owned over the years, flushing every 5 years does the job. Never had a bad overheating problem and each time I flushed brought the engine temps down about 5 degrees.

Scale build up can occur while the boat is sitting if the raw water doesn't drain down which it didn't in most heat exchangers on my Yanmar 6LY. But running the engine and bringing a fresh batch of Ca and Mg laden water causes more scale formation.

So it is a combination of calendar and running time.

David

 

[kchace]

I did mine with Barnacle Buster 5 years ago and its still good. So maybe every few years at the most? Maybe once a year or so if you can open the end of a heat exchanger and visually check the tubes you should be able to tell when its time to redo.


Ken

 

[Dougcole]

Ok thanks guys. That's sort of what I was thinking, but I wasn't sure. My HEs still look good, I'm more concerned about the oil coolers and transmission coolers, which I can't really crack into.

 

[Comodave]

I would guess between 3 and 5 years. I flushed mine a couple of years ago so probably another 3 years for me.

 

[DavidM]

Oil and transmission coolers are usually further down the R/W circuit with the main heat exchanger being first. If the main heat exchanger is clean then the others are likely clean as well.


David

 

[firehoser75]

I am a strong believer in the value of regular freshwater flushing. I flush my raw water cooling system as often as I can after a run (in other words, every time I can access a decent supply of clean dock water). I store my engine over the winter (about 5 months) with the system full of a potion of "salt away" in freshwater. I do not use any other products.
However, I do not believe just flushing (either freshwater regularly or using BB every few years) eliminates the need for a regular (every 5 years or so if properly, regularly flushed) off engine service. If you are a comfortable DIYer you can acid soak the components at home to clean out the raw water deposits, but you also need to pressure test these components to ensure that there are no damaging leaks.

On my engine, the raw water path goes from pump to fuel cooler (which I have removed permanently), aftercooler, gear oil cooler, and finally the engine heat exchanger and out to the exhaust. Without the good care and the somewhat regular pressure testing, how can you be sure that you are not developing any leaks where you could be adding saltwater to your fuel tank(s), engine air intake, transmission oil, or into the engine coolant? Prevention is far better than finding out after a leak has occurred. If you are not a DYIer, with the exception of the aftercooler, all of the cooling items above could be taken into a radiator shop for cleaning and testing at a minor (boating) cost.

Even with freshwater flushing, I think it is prudent to service the aftercooler "off engine" every 4 years so it can be cleaned (both raw water and air side), O rings replaced, and regreased up to help prevent future corrosion (that can be a real problem what with the dissimilar metals contacting each other in a salt water environment). Then the critical pressure test prior to reinstalling back on the engine.
Tony Athens recommends an at most 2 year service cycle for aftercoolers if they are not freshwater flushed regularly.
So in a nutshell, I don't think an occasional flush with BB is THE answer. It can prolong the time between fully servicing the components, but it is not "covering all the bases" IMHO.

 

[catalinajack]

Don't buy Barnacle Buster. It's just phosphoric acid at a concentration of no more than 10% per the MSDS on their website. On Amazon, it costs $75/gallon. Phosphoric acid at Home Depot (USA) costs $18 at a concentration of 35%. That makes the Barnacle Buster at least $225/gallon.

 

[rslifkin]

Personally I only flush heat exchangers with anything more than water if cooling performance starts to become inadequate. No reason to potentially wear the metal in the heat exchangers if they don't need it.

 

[Comodave]

I used BB the first year we owned the boat to start a history. The temp on one engine went down 5 degrees and the other engine went down 10 degrees.

 

[Dougcole]

I didn't notice a temp difference when I flushed mine. I did get a lot of black gunk out of the engines though.


Thanks for the advice on the oil coolers etc., David. That makes a lot of sense.


I pulled my intercoolers and had them rebuilt right after I did the system flush. I'm not running hot or anything, I just like to stay ahead of this kind of stuff.

 

[Arc]

Just use your boats. Nature will flush it for you.

 

[catalinajack]

And that is precisely why the Barnacle Buster product employs phosphric acid. It does not attack or wear away the innards of coolers or heat exchangers. Muriatic acid not recommended. Perhaps frequent fresh water flushing will keep the exchangers clean but many boats are not set up to do so nor do their owners care to do it however easy you may find it. Personally, flushing every damn time I stop the boat is far too much bother. A good cleaning with phosphoric acid every two years works fine for me. To each his own.

Personally I only flush heat exchangers with anything more than water if cooling performance starts to become inadequate. No reason to potentially wear the metal in the heat exchangers if they don't need it.