How to Mount a Swim Ladder on a Boat

Written by erin harty
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How to Mount a Swim Ladder on a Boat
Boat ladders with metal rungs instead of flat steps can be uncomfortable on the feet. (echelle de bateau de plongée sous marine image by KALISTE A from

Transom swim platform-mounted ladders give an outboard motor boat more versatility. Ladders offer a way to bring in water-skiers and swimmers quickly and without injury. Permanent ladders are hinged or telescoping so the ladder can be shortened and out of the water when not in use. Install a swim ladder on dry land for ease of installation and so the sealant can cure properly.

Skill level:

Things you need

  • Aluminium backing plate
  • Electric drill
  • Drill bits
  • Marine adhesive/sealant
  • Level
  • Stainless steel bolts (longer than the thickness of transom and back plate combined)
  • Stainless steel washers
  • Stainless steel locknuts

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  1. 1

    Measure where the waterline is when the boat is at rest. Mark this line. There should be at least two steps underwater and one above when in use. The ladder has to extend far enough to comfortably get a foot on the lowest step.

  2. 2

    Choose a spot on the transom where the ladder won't interfere with the outboard motor when down. With the ladder in the desired spot, line it up with the waterline mark and then adjust for height. Mark the transom above the top mounting hole of the ladder.

  3. 3

    Line the backing plate up to the previous markings and using it as a template, mark the holes through the plate onto the transom. Drill holes through the markings. From the inside of the transom, apply marine sealant to the back of the plate and line the plate up with the holes. Add more sealant around the holes before and after securing bolts.

  4. 4

    Measure the width between the swim ladder brackets and mark the transom just below the top bolts from the mounting plate. Use a level to ensure that the brackets are mounted straight. Drill the appropriate holes through the transom and mounting plate and secure the bolts with marine adhesive, washers and locknuts.

  5. 5

    Screw the swim ladder to the brackets. Use the hardware that came with the swim ladder and secure the ladder to each bracket.

Tips and warnings

  • The swim ladder should extend into the water. Depending on the angle of the boat's transom, you may need to install a standoff extension to keep the ladder vertical. This can be installed in the mounting plate and then secured to the ladder.
  • Choose a ladder with flat treads rather than metal rungs. The flat treads allow for more traction and are more comfortable.
  • A permanent, transom-mounted swim ladder should be folded up when not in use. If left in the water it can create drag and sustain damage.
  • Check the transom swim platform for strength. If the material doesn't look like it can withstand the stress of the weight on the ladder, it can be reinforced from the inside with a thicker backing plate.

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