The Ultimate Guide To Blocking Your Boat

Putting a boat on blocks is a tricky task that requires careful execution to avoid damage to the boat and injury to oneself. The process involves using a combination of blocks, jacks, and stands to elevate the boat and remove the trailer. It is important to select a firm and level surface to work on and to use the appropriate equipment for support. While concrete and wooden blocks are commonly used, wooden blocks are generally recommended to avoid potential damage to the boat's gel coat. Safety precautions, such as having an extra pair of hands and using a pulley system for control, are also emphasized by those with experience in the process.

Select a firm, level surface

Selecting a firm, level surface is crucial when putting a boat on blocks. The surface should be perfectly flat and hard to ensure the boat is stable and secure. Look for a level piece of ground that is free from any inclines or soft spots. If you're blocking the boat on an asphalt driveway, it's important to put down plywood first to prevent the stands from digging into the asphalt as the temperature rises. Concrete surfaces can also be used, but be aware that the weight of the boat may cause the concrete to crack over time.

When selecting a location, consider the size of your boat and the number of blocks you'll need. For larger boats, you may require more blocks and stands spaced every six feet. Ensure there is enough space to manoeuvre the boat and trailer and allow for easy access to the boat's underside for repairs or maintenance.

Safety should be a top priority when blocking a boat. Choose a location that is free from hazards and has good traction to prevent slipping. If possible, have an assistant to help guide and stabilise the boat during the blocking process. By selecting a firm, level surface and taking the necessary precautions, you can ensure the process of putting a boat on blocks is safe and efficient.

Additionally, the surface you choose should be close to where you plan to store your boat. This will save you the trouble of having to move the boat a long distance after it has been blocked. If you are blocking the boat for storage, make sure the surface is sturdy enough to bear the weight of the boat for an extended period.

Overall, selecting a firm, level surface is a crucial step in putting a boat on blocks. By choosing a suitable location and taking the necessary precautions, you can ensure the safety and stability of your boat during the blocking process and subsequent storage or maintenance work.

Use a roller trailer

If you use a roller trailer, you should block up the boat for winter storage. If you don't, the rollers may leave small indentations in the hull and possible stress cracks in the area of the pressure points. The rollers straddle the main stringer of the hull; they don't sit on the stringer like a bunk trailer.

Look for 12" x 12" pressure-treated wood blocking. Do not use cinder blocks if you’re working on the bottom of the hull. If you can’t find the correct size blocking, you can use 6" x 6" pressure-treated wood and glue four pieces together with Liquid Nails. Then, nail 12" x 12" x 5/8" plywood to the ends to make them one 12" x 12" unit and to keep them square and locked in place.

When blocking up a boat, do not use a three-point blocking stance. For an 18-foot boat, you should have two main blocks under the boat and two boat stands on the port and starboard sides for a total of six contact points. Bigger boats require more blocks and boat stands (every six feet). So, you will have eight contact points on a 25-foot boat.

Make sure you tap the bottom of the hull to find the inside supports so you know where to place the blocking. If placed in the wrong areas, the blocking can go through the hull. The boat stands are used just to keep the boat balanced and level. The main weight of the boat always sits on the wooden blocking.

Blocking up a boat on a roller trailer is a good idea, especially for winter storage. By following the steps outlined above, you can ensure that your boat remains in good condition and is properly supported during the off-season.

Prepare the necessary equipment

To prepare the necessary equipment for putting a boat on blocks, you will need the following:

• A firm, level piece of ground to place the boat. Look for a flat surface that is sturdy and even, ensuring it can bear the weight of the boat.
• Blocks to support the boat:
• It is recommended to use wood blocks such as pressure-treated wood blocking or lumber. You can opt for 12" x 12" blocks or glue four 6" x 6" pieces together to form a larger block.
• Avoid using cinder blocks or concrete blocks as they can be unsafe and damage the boat's gel coat or hull.
• Ensure you have enough blocks to support the boat securely. For an 18-foot boat, you'll need at least two main blocks and two boat stands, while a 25-foot boat will require eight contact points with more blocks and stands.
• Jack stands or boat stands to help balance and level the boat. These are adjustable and can be purchased new or used.
• A hydraulic jack or floor jack to lift the boat. A small hydraulic jack can fit under the centre of the transom, while a larger jack may require additional wood to protect the hull.
• Wood pads or plywood:
• Use wood pads between the blocks and your boat to protect the hull.
• If blocking on an asphalt driveway, place plywood under the stands to prevent them from digging into the asphalt.
• Additional tools:
• A hammer to tap the bottom of the hull and locate the inside supports.
• Masking tape to mark the support areas on the hull.
• A winch and winch cable if using a trailer.
• Rope or straps to secure the boat to a sturdy anchor like a tree.
• Bottles jacks or other lifting equipment.

Gather all the necessary equipment and carefully lay it out before beginning the process of putting your boat on blocks. It is crucial to prioritise safety and stability when selecting and preparing your equipment.

Position the boat

Positioning the boat correctly is crucial for successful and safe blocking. Begin by selecting a firm and level piece of ground to place the boat. Back the boat and trailer into position, ensuring there is enough clearance to work with. Let out a few feet of winch cable and push the boat back off the trailer until it reaches a balance point—where adding a little weight at the transom would cause it to tip back and slide off if not for the winch cable.

Next, stack blocks under the transom corners and the keel. It is recommended to use masonry blocks, with a pad of plywood underneath if the ground is soft. The American Boat and Yacht Council (ABYC) advises against using cinder blocks and suggests cribbing for blocks stacked higher than two tiers (stacking adjacent tiers perpendicularly). The height of the stack should not exceed 1.5 times the length or width of its base, whichever is shorter. Use a piece of wood as a protective pad between the stack and the boat.

Now, with the help of an assistant, carefully tip the transom onto the blocks. Gently pull the trailer forward until the boat is supported by the blocks at the back and the trailer at the front. Continue stacking blocks along the keel and aft of the stem, ensuring the cockpit can drain. Pull the trailer out from under the boat.

For added stability, the ABYC recommends a minimum of two sets of keel blocks per boat. Place these, and adjust athwartship trim, using more blocks and wood shims, or adjustable jack stands. Refer to the boat manufacturer's guidelines, if available, for preferred block placement. If guidelines are not available, identify areas where bulkheads are installed and place blocks there to distribute the load effectively. Minimum keel block sizes recommended by the ABYC are 4" x 18" for boats under 30 feet and 6" x 18" for boats up to 40 feet. Blocks measuring 12" x 12" are acceptable for any boat size.

Remember, even a small boat is heavy enough to cause serious harm or injury, so always exercise caution and seek professional help if you have any doubts.

Pull the trailer out

Pulling the trailer out is the final step in putting a boat on blocks. Before you get to this stage, you will have already blocked up the boat on a hard, level surface, removed the strapping, tie-downs and jacked up the boat. Now, you can slowly pull the trailer out from under the boat.

This is a delicate process and requires careful attention. If you are using a hydraulic jack, you will need to stop at each crossmember and axle, placing another jack behind each one before removing the previous one. This is to prevent the boat from falling back onto the trailer and causing potential injury. It is also important to have someone help watch the jack during this process.

Once you have pulled the trailer out, you can place boat stands on either side of the boat and lower and remove the hydraulic jack. The boat should now be sitting securely on the blocks and stands.

Frequently asked questions