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Coast Guard and ABYC to Establish Protocol for Testing Prop Guards

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Working with the American Boat and Yacht Council, the U.S. Coast Guard's Office of Auxiliary and Boating Safety has announced a test procedure that aims to gather data about the effectiveness of propeller guards in a standardized and repeatable manner.

"The report provides the means to evaluate the boat performance characteristics and the level of protection of personnel in the water resulting from the installation of a propeller guard on a particular stern-drive or outboard-powered recreational boat," said Phil Cappel, chief of the Recreational Boating Product Assurance Branch.

A look inside the testing tank with the simulated ballistics leg extended toward an exposed propeller.

A look inside the testing tank with the simulated ballistics leg extended toward an exposed propeller.

The test procedure was developed through comprehensive on-water testing of various available propeller guards to compile evaluative performance criteria and laboratory testing of the personnel protection capabilities of these same propeller guards.

Past test results have varied largely depending on who was doing the testing; something the ABYC is seeking to eliminate.

Along with added safety prop guard manufacturers claim the guards increase a boat’s performance and fuel consumption.

However, engine manufacturers OMC and Mercury Marine have found the guards work well only on slow moving boats travelling about 10 knots or less. furthermore, the faster the boat is moving the more the guards reduce speed capabilities and increase fuel consumption.

“There really wasn’t anything out there that portrayed the performance or maneuverability of a boat, with and without a guard,” ABYC president John Adey told Trade Only Today. “It’s a non-accident-specific test and first of its kind. The idea is that the guard manufacturers would test their guards before putting them to market. Everyone gets evaluated the same way, which is a breakthrough.”

Adey reported that most consumers assume a prop guard will save your life in all situations. While preventing prop related accidents certainly sounds enticing, marine manufacturers have an opposing view of the safety devices.

 Three main types of propeller guards provide varying levels of protection and performance.

Three main types of propeller guards provide varying levels of protection and performance.

A prop guard is simply, and sometimes crudely, a piece of metal affixed to or around a marine engine’s propeller.

Adding flat, directional pieces to vessels’s propulsion unit can cause buoyancy and steering issues and compromise a vessel’s ability to get up on, and maintain plane.

Hydrodynamically, any vertical piece underwater will act as a rudder, while anything horizontal will act as a planing surface; inevitably effecting the vessel’s handling capabilities while underway.

According to John McKnight, director of environmental and safety compliance at the National Marine Manufacturers Association, it is for these reason the NMMA originally opposed testing of the devices.

The most important factor the testing looks to uncover is the effectiveness of different types of guards.

ABYC testing uncovered that cage style guards to a good job of protecting people in the water, and have minimal effect on consumption on a slow moving boat. However, as speed increased, the boats maneuverability deteriorated. The large, fast-moving objects the cages created raised concerns for blunt force trauma injuries that could be more fatal.

Other, more minimalistic guards seem to cause less maneuverability issues at high speeds; but provide far less protection to people in the water.

Keith Jackson, a partner at Maritect Industries in Redding, Calif., does not think propeller guards are ideal for all applications. Jackson helped develope a prop guard used by the San Francisco police dive boats, vessels that operate at low speeds almost constantly.

Though the effectiveness of prop guards is still largely open for debate, the new Coast Guard testing procedure is a big step to finding the answer.

“Everybody will make claims about what their product will or won’t do,” Jackson said. “If you’re a developer of guards and you don’t know how to test it appropriately, you might cause more harm than good.”

The diagnostic test equipment required for the performance testing will be made available on a loan basis to interested parties on a first-come, first-served basis for the cost of shipping and insurance.

“Every product has limitations, and that’s okay, as long as you educate the consumer,” Jackson said.

Diagram of the testing procedure and provided equipment

Diagram of the testing procedure and provided equipment