Q: If you've been keeping up with local news, you've probably heard or read that Washington State Ferries has troubles on its hands with the system's four Steel Electric Class boats.

Simply put, the 80-year-old vessels' hulls are falling apart.

So, have those vessels been running all these years on electricity? Why, asked Charles Reed of Kenmore, are they known as Steel Electric Class ferries?

A: For one thing, the hulls are made of steel. For another, those boats are powered by diesel electric propulsion. The diesel engine turns a generator which produces electricity. That electricity is then fed to a motor which turns the propeller, according to ferry folks.

Longtime ferry historian David Black of Poulsbo, himself a former ferry employee, says there was a class of wooden boats called the wooden electrics, and when new boats were made of steel and had a diesel electric engine, they became the steel electrics. Simple enough?

The ferry system's four troubled boats — Illahee, Klickitat, Quinault and Nisqually — were some of the oldest ferries still in service. They've been in the fleet here since the 1950s.