We would never depend on a ship's wheelchair.
Most have non-removable arm and leg rests, which would make transfers nearly impossible for us. They are heavy E&J "clunkers" for the most part. If you truely are dependent upon a wheelchair for all your mobility (not just for convenience) you cannot depend on a ship's wheelchair. In addition, most people who use wheelchairs full time need a fairly custom manual wheelchair that is designed to meet their needs for posture, function and pressure reduction...to use a borrowed chair risks pain, decreased independent and the risk for pressure ulcers. Leave these to the partially or part-time ambulatory.