Zincs on 6/71 Naturals ??

[mariah]

I have 2 6/71 naturals on my 58 LRC. A mechanic told me I need to only put a zinc in the one place after the heat exchanger. He said to leave the other 2 with no zinc?? (one at salt water pump and one before heat exchanger). Is this correct. ???

[Will]

Mariah,

Zincs are cheap compared with the cost of replacing hardware eaten away by electrolysis. I’d think the most important ones are those located in low points and submerged in water most of the time.

Sometimes people avoid installing zincs in locations where they can break or have pieces flake off and clog up intercoolers and heat exchangers (in your case the sea water pump and on the inlet side of the heat exchanger). However, if you check them frequently (I do mine quarterly), you can remove deteriorated material or replace them before the zincs break away from the threaded plugs.

Will

[REBrueckner]

Tough question to answer. I'd stick with using zincs at most spots.

I personally believe 90% of engine zincs wear away from water erosion rather than galvanic protection but I use them anyway. Wil is correct that zincs closest to the intake strainers are important because any protective current is hampered by narrow water passages. It introduces higher resistance. Hose connections isolate most components in contact with seawater which further limits galvanic corrosion...
However, stray current corrosion (due, say, to a wet bilge wire) could adversly effect an engine and if an zinc is present it MAY help prevent corrosion damage, but that's not guaranteed. Almost all engines are bonded to other underwater metals and used as the ground for both AC and DC circuits...and used as a path for alternator charge current as well. Zincs from the bonding system are too far removed from the engines to be of a protective value.

So the continued use of at least some engine zincs is likely a good choice. An electrically isolated engine with insulated ground alternators would likely be less likely to need such protection.

On my 8V71TI's, I just mentioned to my mechanic my heater exchanger zincs are out of the water (engine off) ....I know because when I check them, no water runs out...He pointed out that the impeller blocks intake water from leaking and the turbo/exhaust dumps are high to block that end..so it should stay full of water...well, it never has on either engine since I've had the boat....

If you have ever inspected heater exchangers, intercoolers,etc...you'll find a few parts mussel shell and a few parts zinc pieces....very annoying...but perhaps the lesser of alternative evils.

[mariah]

Thanks for the info!! I am going to put all new zincs in and check bi-monthly.

[outbound]

On my 6-71n's the zincs are mounted in the engine heat exchanger and the fuel cooler. I put new ones in every spring and in august. They seem to wear out rather than erode. Jack