DOCK-TIONARY: MARINE PROPULSION TECH
Welcome back to Dock-tionary, where we help ferry fans learn how to speak boat. This month, we’re explaining the difference between the two different types of engine propulsion we employ on our vessels systemwide.
When it comes to marine vessels, there are two main types of engine propulsion - propellers and water jet engines. Jet boats use an engine to create a jet of water and force it out of nozzles at the rear of the vessel. Propeller vessels utilize engine power which control a propeller that is used to thrust the boat forward and backward. Most vessels with propeller propulsion perform better, make cleaner wakes, and provide higher fuel efficiency than boats that employ jet engines.
There are pros and cons to employing each type of engine. Propeller propulsion has become the more popular option in the marine industry and especially for bigger vessel types including some vessels in our ferry fleet. When it comes to jet propulsion engines (or jet boats), vessels with this type of propulsion can travel faster through water, operate in extremely shallow conditions, and can accelerate at a faster rate. Ferry vessels that operate primarily on the Vallejo route employ jet engines due to the longer route length enabling the trip to be done in an hour.
On the downside, propellers are susceptible to warping and bending due to debris, or entanglement with fishing lines. Water jets can be clogged by debris in the Bay. For both types of ferries, this is especially an issue this time of year when storms push fallen trees and large branches down into the Napa River and Oakland Estuary.
Right now, San Francisco Bay Ferry employs 10 propeller boats and six jet boats. See if you can figure out which one you’re on the next time you ride.
