Heat Exchangers and Oil Cooler cleaning

"Getting a late start to the s

"Getting a late start to the season and want to give the cooling system a good flush while on land. Will disconnecting the hoses of the U-cooler and flushing with fresh water be suffice or do I need to go further? This is also the first I have heard of Zinc in the U-cooler and heat exchangers. was going to open the end caps of the heat exchangers and flush the same. The boat is an 88 Blackfin with twin 454's. Any help is appreciated, scheduled to splash it on friday. Thanks."

"Here is my experience: The O

"Here is my experience: The OEM U oil cooler has a lower bronze casting that narrows at the zinc pencil location. This has the effect of increasing the water velocity in that area, which then increases the zinc erosion onto the internal surfaces of the little raw water copper tubes. I've rebuilt several of these coolers; they all had significant build up of this zinc. Note that it is not loose pieces or chucks of metal; it's more of a fine, hardened formation of the material. It cannot be flushed out with water, but it does knock off with a dull screwdriver, once you open up the assembly. It takes basic sweating skills to do this successfully. I would also replace any U cooler over 10 years old, subject to salt water. Salt water getting into either the engine or transmission is something you don't want.
Also, I don't see the same effect with the HE; but it does clog with loose zinc and also subject to a buildup of scale."