Gary,

I was in New Zealand and could not buy acid because it requires a special license...I had a marine engineering shop do it for me.

However, I did acid-wash the heat exchanger core on the Yanmar using On-Off which is a combo of hydrochloric, oxalic and phosphoric acids. I let the heat exchanger core soak in the On-Off for about 5-10 minutes until it was visibly clean. I then rinsed it with fresh water and soaked it in a bucket of baking soda and water to neutralize any residual acid.

A side note about On-Off: On-Off is advertised as a hull cleaner, but is also an excellent metal cleaner and rust remover. DO NOT USE it on chrome plated turnbuckles or chrome plated winches as it will remove the chrome.

Hope this helps.

Bill
BeBe SM2k, #387