You want the water to come to a full, rolling boil so you won't have to leave the plums in the hot water for too long. If you over boil them, they'll get mushy.
[header] How to peel plums [title] Boil a pot of water. [step] The pot should be large enough to hold at least four or five plums. Use enough water to allow you to submerge the plums completely.