2000 Yamaha 225 OX66 not holding prime,

[smzdano]

2000 Yamaha 225 ox66 not holding prime.
Replaced filter housing and priming bulb but still not holding.

 

[seasick]

If the needle valve in the VST is not sealing, you will loose prime but before I assume that is the issue, do you loose prime when motor not running or when it is running. The later is a whole different story.
If the primer bulb does not collapse but goes soft when running, you have an air leak most likely. If the primer bulb collapses, you have a blockage in the fuels line, pickup or vent.

You also mentioned you changed filter housing. What exactly did you replace? There are multiple filters on your setup.