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Merc 500 Outboard fuel pump

tbarr2020

New member
I recently replaced the fuel pump diaphragm and check valves on a merc 500. I thought the check valves were identical so I didnt pay attention which on went where, only that they were placed properly to allow fuel flow. After inspecting the only check valves I noticed they are labeled "1" and "2". Ive seen this on another mercury outboard that I recently replaced the check valves on also. Are these check valves identical? why are they number? Do they have different springs or something? The repair manual makes no mention that there is a difference.
 
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