Is there any danger in replacing a anti siphon valve? Boat is full (50 gal.).

It should be above the gas level in the tank. I've changed many; haven't had any issue.

Thank you! Was a little worried about causing any spark etc. unscrewing it. I know it should not. Our 9 year old boat is doing same thing others have described. Changed primer bulb and cannot get it pumped up still so I’m assuming it may be anti siphon valve..
then it falls on its face as we are coming up on plane. One friend suggested VST service but since it appears to be not getting fuel from tank I will start there.

Primer bulb ??? That is a non zero OEM install for I/O s actually its USCG not compliant. Those are for outboards and installed in a non enclosed area.

There should be no primer bulb installed for I / O s so I have to ask -- do have an outboard engine app on your boat ??

This is a Yamaha 150 4 stroke on a 2010 Hurricane 220 SD.