Fuel prices continue to soar and there never seems to be enough time for boating, rest, and relaxation. So, if I could give you one piece of advice on how to save fuel, money, and time while boating, I’d tell you to “go with the flow.” Awareness of currents and using them to your advantage make you a smarter boater.
My apologies to lake sailors who don’t see much more than wind-driven currents, but anyone boating on a river or in waters affected by current should be able to relate. Here’s an example from the venerable Eldridge’s Tide and Pilot Book current tables: Using a hypothetical fuel cost of $4/gallon, a vessel burning 10 gallons of fuel an hour at a speed of 8 knots travels 24 miles to her destination against a 2 knot current. Her speed made good (SMG) is 6 knots and she arrives in 4 hours having burned 40 gallons of fuel with a fuel cost of $160. If the owner of this vessel had waited for a favorable current they would have made a SMG of 10 knots and arrived in 2 hours 24 minutes with a fuel cost of only $96. The time saved, 1 hour 36 minutes, allows more time for relaxation and the $64 saved could buy a nice meal ashore.
I highly encourage you to obtain current charts for your area. Every self-respecting mariner should have a copy of the local tide and current tables aboard. (Eldridge has been the bible for the East Coast of the US for 136 years.)
Learning how to read currents on stationary objects like buoys as well as from your electronics is helpful. Also, learn the language associated with currents. For instance, Ebb or Flood currents should be qualified by the direction toward which the current is flowing. To be perfectly correct, the title of this blog should be in and out with the current, since currents are horizontal and tides vertical.
Tides are astronomical events, primarily related to the gravitational effects of the moon. Tides are higher, and currents stronger, during full and new moons. However, high tide does not necessarily correspond with zero current, and while irretrievably connected, the difference between the time of current change and time of high or low water have more to do with geography. For these same geographical reasons, there is also no correlation between tidal range and current strength. As an example, Boston, MA has a tidal range of 9.6 feet and max currents of about 2 knots, while Woods Hole, MA has a tidal range of only 2 feet, but currents that can exceed 7 knots. Remember that tide and current tables are predictions of average conditions and that weather can also affect tides and currents dramatically. So learning more about the height of the tides and strength of the currents is not just a safety issue, but a practical boater’s free guide to saving time and money.