Well, if you sealed every hatch and vent and any other hole in the boat....... then yes, in the highly unlikely event that you somehow capsized your O'Day 23...... she should still float. However, in normal sailing conditions a 23' boat with 1200# of cast iron ballast is unlikely to capsize, I won't say it is impossible..... but it is HIGHLY unlikely without your having done something incredibly stupid while sailing in winds a lot stronger than most of us would sail in.
An O'Day 23 might suffer a "knockdown", that is get hit by a sudden gust of wind and be pushed over nearly on her side... but usually the keel will force the boat upright rather than going over like my DS II could. In 38 years of sailing our CAL 21 which was "self-righting" like the O'DAY 23, we were knocked down only once or twice on windy Buzzards Bay. We half-filled the cockpit with water (my feet got wet!) but the boat righted before much water (less than a gallon or two!) got below (water entered through a vent inside cockpit.). On my DS II I have been knocked over enough to take water over the lee side only a few times in the last 13 years. The secrets are to release the mainsheet when a gust hits and the jib too if needed (I've never needed to let go of the jibsheet, but then in gusty winds I most likely would not have the jib up) and too reef the mainsail if needed.
On a keel boat like the 23 one should luff up in gusts by turning slightly into the wind to spill the wind from the sails, and perhaps release the mainsheet in a strong gust. Also, if you feel that a knockdown is possible given the conditions; close the hatches and the companionway slide (door). A 23 would need to stay on her side for a while (or have a hatch wide open!) to risk filling and sinking in a knockdown, and releasing the sheets as the boat heels over should allow her to come back up before that happens.
If a strong gust hit and layed a 23 over on her side with hatches open and the gust was sustained for long enough, the boat will fill with water and most likely sink.... as I recall the 23 did not have positive floatation. However, as I say.... you would have to do absolutely EVERTHING wrong to find yourself in that dire of straits.
