RINSE clean plastic containers and lids with boiling water. Dry thoroughly.
PEEL and pit mangos. Mash fruit. Measure exactly 3 cups into large bowl. Add lemon juice and sugar; mix well. Let stand 10 minutes, stirring occasionally.
MIX water and pectin in small saucepan. Bring to boil on high heat, stirring constantly. Continue boiling and stirring 1 minute. Add to fruit mixture; stir 3 minutes or until sugar is dissolved and no longer grainy. (A few sugar crystals may remain.)
FILL all containers immediately to within 1/2 inch of tops. Wipe off top edges of containers; immediately cover with lids. Let stand at room temperature 24 hours. Jam is now ready to use. Store in refrigerator up to 3 weeks or freeze extra containers up to 1 year. Thaw in refrigerator before using.