Complex sentence: These boats had a range of 140 miles when cruising at 24 knots, and could achieve a top speed of 29 knots, as even faster boats became available many of the ST 200s were converted into fireboats.
Split into simpler sentences: These boats had a range of when cruising at, and could achieve a top speed of. As even faster boats became available many of the ST 200s were converted into fireboats.