Bimini Top and Boat Cover Buying Guide: How to Measure and Choose
Quick answer: For a bimini top, measure the mounting width (outside to outside across your mounting points) first, then pick the height and length you want. For a boat cover, measure centerline length (bow tip to transom) and beam width, and choose a cover rated for how you use it: storage, mooring or trailering. Pick solution-dyed acrylic or marine polyester fabric that resists UV and mildew.
Shade underway and protection at rest are two of the best upgrades for any boat. A bimini turns a scorching Florida afternoon into a comfortable day on the water, and a good cover keeps sun, rain, leaves and bird droppings off your upholstery, electronics and gelcoat. The catch is fit. A bimini that is the wrong width will not mount, and a sloppy cover pools water and blows off. This guide walks through measuring, choosing fabric and frames, and getting it right the first time.
Part 1: Bimini tops
Step 1: Measure the mounting width
Measure straight across the boat between where the bimini frame will mount on each side, outside to outside. This is the single most important number. Biminis are sold in width ranges (for example 79 to 84 inches), and you want your measurement to fall inside the range.
- Deck mount: measure across the deck at the gunwale where the hinges will go.
- Rail mount: measure across the rails, outside to outside.
- Side mount: measure across the inside of the hull sides.
Step 2: Choose height
Measure from the mounting point up to where you want the top. Taller tops give more headroom when standing, but catch more wind and may not clear a garage or lift. Most runabouts use a 46 to 54 inch frame height.
Step 3: Choose length
Length is how much fore-to-aft shade you want. Longer tops shade more of the cockpit, but must clear the windshield, motor and anyone at the helm. A 6-foot length is common for bowriders and center consoles.
Step 4: 3-bow or 4-bow?
- 3-bow: the most common. Lighter, folds compact, fine for most boats under 22 feet.
- 4-bow: longer coverage and more support, better for bigger boats and pontoons.
Use front and rear straps to keep the top stable at speed, and fold it into its storage boot when trailering at highway speeds.
Part 2: Boat covers
Step 5: Measure the boat
- Centerline length: from the tip of the bow straight back to the transom, over the deck centerline. Do not include the swim platform, outboard or bow pulpit.
- Beam: the widest point of the boat.
- Note the hull style (V-hull, bass boat, pontoon, deck boat), windshield type, and anything that sticks up, such as a trolling motor, T-top, ladder or bow rail.
Step 6: Choose a fit and rating
| Cover type | Fit | Best for |
|---|---|---|
| Universal | By length and beam range | Budget, short-term storage |
| Styled-to-fit | By hull style and size | Most owners, good fit at a fair price |
| Custom | Exact boat model | Best fit, highest cost |
Check the rating too. A storage or mooring cover is for the dock or the driveway. A trailerable cover has tie-downs and reinforcement to survive highway speeds. A storage cover will shred on the interstate.
Step 7: Prevent pooling
Water pooling on a cover stretches fabric, breeds mildew and can tear it. Use a cover support pole or support system to create a peak so water runs off, and tension the cover with straps or rope ratchets.
Choosing fabric
- Solution-dyed acrylic: color is in the fiber, so it resists fading, breathes well and lasts the longest. The top choice for biminis.
- Solution-dyed polyester: strong, water resistant, a good value for covers.
- Coated polyester: lower cost, less breathable, shorter life in hard sun.
In Florida and other high UV areas, cheap fabric often fails in one or two seasons. Paying more for solution-dyed fabric is almost always worth it.
Our picks
All in stock at Boat Supplies Direct.
Complete bimini tops
Carver 3-Bow Bimini Top with Boot, Black Acrylic, also in Pacific Blue and Cadet Grey.
Replace the fabric or the frame
Carver 3-Bow Acrylic Bimini Fabric and Boot or the Carver 3-Bow Bimini Frame. For mounting, RAILBLAZA Clevis Bimini Supports.
Covers and cover support
Carver Poly-Flex II Styled-to-Fit Cover (16 ft drift boats), the Camco Adjustable Boat Cover Support Kit, and the Carver Boat Cover Rope Ratchet for tension.
Frequently Asked Questions
How do I measure for a bimini top?
Measure the mounting width straight across the boat, outside to outside of the mounting points. Then choose the height from the mount to the top and the length of shade you want. Width is the most important measurement.
What is the difference between a 3-bow and 4-bow bimini?
A 3-bow bimini has three frame bows and suits most boats under about 22 feet. A 4-bow bimini is longer and gives more coverage and support for larger boats and pontoons.
How do I measure my boat for a cover?
Measure the centerline length from the bow tip to the transom, excluding the swim platform and motor, and the beam at the widest point. Note the hull style and anything that sticks up.
Can I trailer my boat with the cover on?
Only if the cover is rated as trailerable and properly strapped down. Storage and mooring covers can tear apart at highway speeds.
What is the best fabric for a bimini top?
Solution-dyed acrylic. The color is in the fiber, so it resists UV fading and mildew, breathes well and lasts the longest.
How do I stop water pooling on my boat cover?
Use a cover support pole or support system to create a peak, and tension the cover with straps so water runs off.
This guide is general information. Always check the manufacturer's size range against your measurements before ordering.
