Complex sentence: The museum's expanding collection of artifacts have increased to make up a collection which includes 250 watercraft, 65 inboard engines, 138 outboard motors and approximately 3000 smaller artifacts as of 2006.
Split into simpler sentences: The museum's expanding collection of artifacts have increased in numbers during the years as well. The boat collections include 250 watercraft, 65 inboard engines, 138 outboard motors and approximately 3000 smaller artifacts as of 2006.