The United States Coast Guard operated four 52-foot Motor Lifeboats (MLBs), also known as "special purpose craft — heavy weather" (SPC-HWX), from 1956 until 2021.

They were withdrawn from service in 2021 and laid up due to the difficulty of maintenance; procurement started in 2024 for their planned replacements (SPC-HWX II), which according to preliminary designs will be 64 feet long, overall.

After World War II, reduced budgets meant the Coast Guard continued to use its two existing wooden 52' MLBs (Type F), which had been completed in 1935.

[5] The Coast Guard bills the 52-foot MLBs, officially designated "special purpose craft – heavy weather" (SPC-HWX), as "virtually unsinkable", with self-righting and self-bailing capabilities and the ability to tow vessels as large as 750 long tons (760 t) in 30-foot (9.1 m) seas.

[9] In November 2021, all four boats were towed to Coast Guard Station Cape Disappointment and laid-up pending a decision on their future disposition.