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What Size Hitch Ball for a Boat Trailer?

Boat trailers show up on two rows of the ball chart, and the coupler stamp picks the row.

Quick answer: A 2 in ball is the most common size for boat trailers and is listed at 3,500 to 12,000 lb (CURT hitch balls). A 1-7/8 in ball is the light-duty size for fishing-boat trailers on cars, minivans, and crossovers, listed at 2,000 to 3,500 lb (CURT hitch balls). Match the coupler first, then confirm the ball's gross rating exceeds the loaded trailer. That rating is gross trailer weight, not tongue weight.

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2 in trailer hitch balls

Ball chart rows that mention boats

FigureValueSource
2 in ball diametermedium duty, most common, includes boat trailersCURT hitch balls
2 in ball gross rating3,500 to 12,000 lbCURT hitch balls
2 in shank length1-3/4 to 3 inCURT hitch balls
2 in shank diameter3/4 to 1-1/4 inCURT hitch balls
1-7/8 in ball, fishing-boat trailerslight duty, cars, minivans, crossoversCURT hitch balls
1-7/8 in ball gross rating2,000 to 3,500 lbCURT hitch balls
1-7/8 in shank length1-5/8 to 3 inCURT hitch balls
1-7/8 in shank diameter3/4 to 1 inCURT hitch balls
Class 3 receiver2 in, up to 8,000 lb grossCURT hitch classes
Tongue weight share of grossabout 10 to 15 percentCURT tongue weight
Brakes and breakaway switchmore than 1,500 lb loadedNHTSA towing safety

How to size it

Start with the coupler on the trailer, not with a guess about the boat. The ball diameter has to match the coupler size, and that size is usually stamped on the coupler (CURT hitch balls). A 2 in ball in a 1-7/8 in coupler is the wrong part even when the weight number looks generous.

Then check the shank against the ball-mount hole. The 2 in ball's shank diameter runs from 3/4 in to 1-1/4 in, and its length runs from 1-3/4 in to 3 in. The 1-7/8 in ball's shank diameter runs from 3/4 in to 1 in, and its length runs from 1-5/8 in to 3 in (CURT hitch balls). If the shank is too small for the hole, the fix CURT names is a reducer bushing. A loose shank is not a fit.

Then read the gross rating stamped for that part number. Ratings vary, and the chart ranges are 3,500 to 12,000 lb for 2 in and 2,000 to 3,500 lb for 1-7/8 in (CURT hitch balls). The number has to exceed the loaded boat plus trailer. It is not a tongue-weight rating. Tongue weight is a separate 10 to 15 percent of gross trailer weight; under 10 percent the trailer may sway, and over 15 percent the vehicle is less responsive (CURT tongue weight). The pound version of that band is on how much tongue weight is safe.

A 2 in ball is the best fit CURT names for most Class 3 hitches, and a Class 3 receiver is 2 in, rated up to 8,000 lb gross and 800 lb of tongue weight (CURT hitch classes). A fishing-boat trailer on a car or minivan is the Class 1 or Class 2 case instead: 1-1/4 in receiver, up to 2,000 lb or up to 3,500 lb. The receiver opening and the ball diameter are different measurements.

Ball mounts for a 2 in receiver

If the loaded boat trailer is more than 1,500 lb, many states require a separate braking system and a breakaway switch (NHTSA towing safety). That test uses loaded weight, ideally from a public scale, not the boat's dry hull weight. Safety chains, required by most states, cross under the tongue, with slack for turns and no drag. Lock the coupler so the latch cannot bounce open on the road.

Trailer coupler locks

The tow vehicle's manual still sets GVWR, maximum trailer weight, maximum tongue weight, GCWR, and GAWR, and the hitch has to match those specifications (NHTSA towing safety). No hitch, and no ball, increases what the vehicle can tow (CURT hitch classes). Check that side on towing capacity explained and in the trailer tow calculator.

Related

FAQ

What ball do most boat trailers use?

A 2 in ball. CURT calls it the most common size and lists boat trailers among its uses, at 3,500 to 12,000 lb gross (https://www.curtmfg.com/towing-accessories/trailer-balls/learn-more). It is also described as the best fit for most Class 3 hitches, and a Class 3 receiver is 2 in (https://www.curtmfg.com/types-trailer-hitches).

When is a 1-7/8 in ball the boat-trailer size?

For light-duty fishing-boat trailers on cars, minivans, and crossovers. That ball is listed at 2,000 to 3,500 lb (https://www.curtmfg.com/towing-accessories/trailer-balls/learn-more). Match the coupler stamp anyway. The diameter on the coupler wins over the kind of boat.

Does the ball rating mean tongue weight?

No. Ball capacity is a gross trailer weight rating, and it has to exceed the trailer's gross weight (https://www.curtmfg.com/towing-accessories/trailer-balls/learn-more). Tongue weight should be about 10 to 15 percent of gross trailer weight (https://www.curtmfg.com/trailer-parts/couplers/learn-more), which is a separate measurement.

How do I know the shank will fit?

The shank has to fit the hole in the ball mount. A 2 in ball uses a shank diameter of 3/4 to 1-1/4 in and a shank length of 1-3/4 to 3 in. A 1-7/8 in ball uses a shank diameter of 3/4 to 1 in and a shank length of 1-5/8 to 3 in (https://www.curtmfg.com/towing-accessories/trailer-balls/learn-more). A reducer bushing is the fix when the shank is too small for the hole.

Compiled with AI assistance from the sources below. Spot an error? Email jpanasuk@gmail.com.

Sources