As we slowed down to idle through a narrow, quarter-mile-long cut between Michigan’s Torch Lake and Clam Lake, I turned over the helm of the 20-foot runabout to my buddy while I took a moment to check for voice mail.
I barely got out my phone when my friend — a newcomer to boating — began swinging the wheel wildly to starboard and then back to port, as the sterndrive-powered bowrider carved a wobbly slow-motion S-course through the pass.
“What are you doing?” I asked.
“I am trying to keep it straight,” he answered in a panicked tone, “but it keeps veering from side to side.”
Ah, I forgot to warn him about this annoying quirk known as low-speed wander. It occurs more frequently with single sterndrives but can also plague boats with single outboards.
After offering him a few words of reassurance, I advised him to not oversteer but instead to try smaller corrections. Within a few minutes, he got the hang of it, and our course became far less torturous.
Experienced boaters know how to correct for low-speed wander, but few know what causes it.
Sterndrives and outboards don’t really have much of a rudder, relying more on directional prop thrust. At low speeds, prop thrust is not as effective as a rudder for maintaining a straight course. And that’s why sterndrives and outboards are more prone to low-speed wander.
Here are four tricks that might help minimize its effects: -Trim up slightly. Trimming the drive or outboard up a bit can minimize the effects of prop torque, and this might help keep the boat on a straighter course.
-Put the tabs down. If you have trim tabs, try putting them down all the way. These can act as horizontal stabilizers to keep the stern from wagging.
-Go to four blades. The greater surface area of a four-blade propeller has a bit more low-end thrust for better steering effectiveness and a straighter course.
-Switch to a dual-prop drive. Admittedly an expensive alternative, a dual-prop drive such as a MerCruiser Bravo Three or Volvo Penta Duoprop has more effective prop thrust for maintaining course at idle speeds.