A lot of boats depend on a large Edson diaphragm pump as a last ditch emergency pump. Pumps are either permanently mounted or bolted to a board stowed at the bottom of a locker. Edson pumps are very simple and very expensive—about $300 list for the aluminum 18-gallon-per-minute model, and about $500 for the 30-gallon-per-minute model, more in bronze. They’re probably the best you can buy. One expects them to work in an emergency.

Last spring, Bill Seifert of Warren, Rhode Island, who manages a fleet of expensive yachts for their owners, dropped by the office with a failed Edson pump. …