Question on 16413A Thermostat Housing & missing check balls

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I have a 1995 5.0L 2bbl 305 V8 Mercruiser with an Alpha One Gen II drive in a Mariah. This merc has the design II standard cooling system and when I took the thermostat housing apart, I found that it was missing the plastic sleeve for the thermostat as well as check ball pin kit (parts 30-98475TI), namely the screw with the nylon balls, springs and nut. Why would someone remove these pieces? Could the removal of these pieces result in overheating at higher rpms?

Thanks in advance!