Boat Owners Association of The United StatesNews Room

May 30, 2019

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Boat Owners Association of The United States
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Boaters Aren't the Only Ones Getting Heavier: Outboard Engines Catch Up

BoatUS says be careful when repowering

BoatUS urges boaters to be aware of engine weight when repowering a recreational boat.
BoatUS urges boaters to be aware of engine weight when repowering a recreational boat.
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WASHINGTON, May 30 2019 – One year ago the U.S. Coast Guard required new recreational boats to have more floatation to support the increased weight of newer four-stroke outboards if the boat becomes swamped. Now the agency is implementing those changes as reported in the Spring 2019 issue of the U.S. Coast Guard Boating Safety Circular. Boat Owners Association of The United States (BoatUS) advises recreational boaters to be aware of this issue when considering repowering an older model year vessel with a heavier four-stroke outboard.

“Repowering with a newer, more reliable, cleaner, fuel-sipping outboard is one way to get more life out of a good boat,” said BoatUS Foundation president Chris Edmonston. “However, after having gone through the recent repowering of a 22-foot center-console vessel with a heavier four-stroke, and seeing first-hand the resulting loss of freeboard and performance, we want to remind owners to consider engine weight. With a potentially heavier four-stroke motor and resulting lower freeboard at the stern, swamping is a concern and your boat may handle differently than with the old engine.” 

If you don’t know the weight of the engine you’re replacing, Edmonston recommends you contact the manufacturer before you repower. A boat dealer or repair facility may also be able to provide that information to ensure that, regardless of horsepower, the engine weights are similar. 

Federal requirements mandate that outboard-powered monohull boats 20-feet and under must be built with enough flotation to keep the passenger-carrying area at or just below the water's surface in the event of swamping or capsizing. The boat must float level. There are no floatation regulations for vessels over 20-feet long.

When these regulations were written in the early 1970s, virtually all outboards suitable for smaller boats were two-stroke models covering a broad range of horsepower, but that’s no longer the case. Four-strokes come in virtually every size now, making them viable candidates for installation on more boats. While recently there have been some two- and four-stroke models with comparable power and weight, by and large four-stroke outboard engines remain heavier. A four-stroke’s more complex valve systems typically add 10% to 15% or more weight than their two-stroke counterparts. Twin engine installations compound the weight problem.

This isn’t the first time the Coast Guard has recognized a growing vessel weight issue and updated regulations. In 2011, the “Assumed Average Weight Per Person” was increased from 140 to 185 lbs., but only for commercial passenger vessels. Existing formulas for weight capacity on recreational boats were considered adequate and did not change.


Suggested Tweet and Facebook post:

Thinking about repowering your older boat? BoatUS cautions to watch the outboard motor weight. @BoatUS

About Boat Owners Association of The United States (BoatUS):

Celebrating more than 50 years, BoatUS is the nation’s largest organization of recreational boaters with more than a half-million members. We are the boat owners’ voice on Capitol Hill and fight for their rights. We are The Boat Owners Auto Club and help ensure a roadside trailer breakdown doesn’t end a boating or fishing trip before it begins. When boats break down on the water, TowBoatUS brings them safely back to the launch ramp or dock, 24/7. The BoatUS Marine Insurance Program offers policies that give boat owners affordable, specialized coverage and superior service they need. We help keep boaters safe and our waters clean with assistance from the nonprofit BoatUS Foundation for Boating Safety and Clean Water. Visit