Prepare canning and jar lids and bring water in the canning bath to a boil.
In an 8-quart stainless steel pot, combine strawberries, pineapple, lime juice and rum. Gradually stir in sugar and butter. Bring to a boil over medium hear, stirring constantly until sugar is completely dissolved.
Increase heat to medium-high and bring to a full rolling boil, stirring constantly. Stir in pectin. Return to a full rolling boil, stirring constantly and boil for 1 minute best to use a timer).
Remove pot from heat and skim off any foam. Let jam cool in the pot for 5 minutes, stirring occasionally.
Ladle hot jam into hot jars, leaving a 1/4 inch headspace. Remove any air bubbles. Wipe jar rims and thread with a clean, damp paper towel. Center hot lids on jars and screw on bands until fingertip tight.
Place jars in canner, making sure they are covered by at least an inch of water. Cover and bring to a gentle boil, process 4-oz jars and 8-oz jars for 10 minutes; process 1-pint jars for 15 minutes.
Remove jars from canner and place on a cloth towel. Let cool for 24 hours, then check seals. Wash and dry jars and store in a cool, dry, dark location.