Heat Exchanger Cleaning

[kmacdonald]

I did a little preventative maintenance on my motor today. The motor is 5 or 6 years old and has 2150 hours on it. The engine wasn't running hot but I wanted to check on the tube stack to make sure nothing was growing in it. I removed the tube stack from the Bowman heat exchanger. I was surprised how clean it was. I soaked it in muriatic acid diluted to about 8% for about 10 minutes. When the bubbling stopped I removed it and rinsed it with fresh water. I even let it sit in a bucket of fresh water overnight. It came out pristine and all tubes looked great. Bowman doesn't put zincs on their heat exchangers and says they are not necessary and I saw no signs of corrosion. I think Ill wait longer between cleanings.

[kapnd]

Don’t forget that your raw water system begins with the intake grating and ends at the exhaust outlet, and the whole thing demands diligent inspection.
Inspection interval is probably listed in the manual, but can be extended if you use a fresh water flush after each use.
For my boat, I replace impeller annually, fresh water flush religiously, and go through the system every third year.

[GordMay]

Originally Posted by kmacdonald

... I soaked it in muriatic acid diluted to about 8% for about 10 minutes. When the bubbling stopped I removed it and rinsed it with fresh water. I even let it sit in a bucket of fresh water overnight. It came out pristine and all tubes looked great...

Be careful, in using Muriatic [Hydrochloric] Acid, on your Hx.

Because calcium carbonate (CaCO3) is the salt of weak acid, any solution, with even moderate acidity, will dissolve the compound.

However, Hydrochloric Acid (Hcl, AKA: muriatic acid) is not recommended for descaling some materials; stainless steel, in particular.
Hydrochloric acid will dissolve most metals [copper is an exception]. While it will easily remove calcium carbonate scale, the chloride ion can cause general corrosion, serious pitting, and stress corrosion cracking, of stainless steel [& titanium].

Inhibitors [& sometimes surfactants] are specific compounds, that are added to commercial cleaning chemicals, like “RYDLYME Marine”, to diminish their corrosive effect, on metals.

[kmacdonald]

Originally Posted by GordMay

Be careful, in using Muriatic [Hydrochloric] Acid, on your Hx.

Because calcium carbonate (CaCO3) is the salt of weak acid, any solution, with even moderate acidity, will dissolve the compound.

However, Hydrochloric Acid (Hcl, AKA: muriatic acid) is not recommended for descaling some materials; stainless steel, in particular.
Hydrochloric acid will dissolve most metals [copper is an exception]. While it will easily remove calcium carbonate scale, the chloride ion can cause general corrosion, serious pitting, and stress corrosion cracking, of stainless steel [& titanium].

Inhibitors [& sometimes surfactants] are specific compounds, that are added to commercial cleaning chemicals, like “RYDLYME Marine”, to diminish their corrosive effect, on metals.

Thanks for the info Gord. The tube stack is all copper so it is OK for this purpose. I would not circulate it thru the raw water system like you would Banacle Buster or Rydlyme.