Yanmar 4BY2 engine zinc longevity

[scross]

For the second year in a row, the lower engine pencil zinc in Our Journey was 100% gone after just 80-100 hours on the engine. The top zinc, both this year and last, still has about 75% of solid zinc left on it.
Is there any reason the lower engine zinc is eroding so fast?
Obviously I’m going to start replacing the lower engine zinc twice a season from now on. It just seems odd that there is such a difference between the upper and lower zinc erosion rates.

 

[SkookumR29]

I see the same differential in pencil zinc depletion on our 6by2; my guess is that the upper heat exchanger does not stay fully flooded when the engine is not running, whereas the lower exchanger perhaps does remain flooded. Regardless, I have typically replaced both every 3 months or so, not based on engine hours.

 

[knotflying]

This is typical. As stated above, the bottom zinc is always in water.

 

[scross]

Thanks Mike and Jerry!
I’ll start checking the lower engine zinc every 3-4 months from now on. Fortunately the lower zinc is easy to access and replace if necessary. Just ordered 4 of the zincs from boatzincs.