Time to replace drive washer?

[Ihncheol Park]

Hi, All,
My 140L scratched brand new Tru Turn 2.5" back plate from last prop loose
(it wasn't running lean, but it did anyway).  The backplate got rough
circles on the back with small chips.
Since the engine was acquired used, I have no idea how find a right time to
replace it. It still has some grooves left, but not sharp.
When do you replace drive washer?

Thanks,

Ihncheol



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