Gas tank vents

[jbone]

I have 2 25 gal tanks that are vented only through the cap. It vents through a 1/8 inch hole by the o-ring on the inside of the cap.
Is this sufficient or should I add external vents?
I have a 850 Speed Demon Marine carb on about 525 hp.
J

[spectras only]

On a new boat , I would put an external vent that lets you know when the tanks are getting full. . Your older boat is fine with the vented caps .Why bother drilling more holes in your boat :idea: