How to Wet Sand a Fiberglass Boat

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Sand­ing a fiber­glass boat is an impor­tant part of the boat restora­tion process. It removes old paint and gel coat, as well as any sur­face imper­fec­tions, to help you achieve a smooth and even fin­ish. Wet sand­ing is the most com­mon method used to sand fiber­glass boats. This arti­cle will pro­vide a step-by-step guide on how to wet sand a fiber­glass boat.

Key Take­aways:

  • Prepa­ra­tion is cru­cial, ensur­ing the sur­face is clean and free from con­t­a­m­i­nants.
  • Use wet sand­pa­per, soak­ing it before­hand to pre­vent sur­face dam­age and achieve a smoother fin­ish.
  • Apply gen­tle pres­sure while sand­ing to avoid harm­ing the fiber­glass.
  • Progress grad­u­al­ly from coars­er to fin­er grits for a pol­ished result.
  • Fin­ish by pol­ish­ing the sur­face to restore shine and pro­tect the fiber­glass.

How to Wet Sand a Fiberglass Boat

Wet sand­ing a fiber­glass boat requires the use of sand­pa­per and water. Start by wet­ting the boat’s sur­face with a hose or buck­et of water and then sand­ing the area with a medi­um-grade sand­pa­per. Be sure to use a block of wood or rub­ber sand­ing pad to even­ly spread the pres­sure across the sur­face. Move the sand­pa­per in a cir­cu­lar motion, grad­u­al­ly work­ing your way up to a fin­er grain sand­pa­per as the sur­face becomes smoother. 

  1. Pre­pare the Area: Begin by prepar­ing the area where you will be wet sand­ing. Ensure that you have a clean and well-lit work­space. It’s also essen­tial to have a water source near­by for rins­ing.
  2. Gath­er Sup­plies: Gath­er the nec­es­sary sup­plies, includ­ing wet sand­pa­per (choose the appro­pri­ate grit for your spe­cif­ic needs), a sand­ing block or sand­ing pad, a buck­et of clean water, and a hose with a spray noz­zle.
  3. Wet the Sur­face: Wet the sur­face of the fiber­glass boat using a hose with a spray noz­zle. This will pro­vide lubri­ca­tion and pre­vent the sand­pa­per from cre­at­ing exces­sive fric­tion.
  4. Start Sand­ing: Start sand­ing the fiber­glass sur­face using the wet sand­pa­per. Use a sand­ing block or sand­ing pad to ensure even pres­sure and con­sis­tent sand­ing. Begin with a low­er grit sand­pa­per to remove any major imper­fec­tions, then grad­u­al­ly move to high­er grits for smooth­ing and refin­ing the sur­face.
  5. Keep it Wet: Through­out the sand­ing process, it’s cru­cial to keep the sur­face and the sand­pa­per wet. Dip the sand­pa­per in the buck­et of clean water fre­quent­ly and spray the sur­face with water as need­ed to main­tain a wet envi­ron­ment.
  6. Check Your Progress: Peri­od­i­cal­ly pause and rinse the sur­face with clean water to assess your progress. This will help you deter­mine if you have achieved the desired lev­el of smooth­ness and removed any imper­fec­tions.
  7. Rinse and Dry: Once you are sat­is­fied with the sand­ing results, thor­ough­ly rinse the boat’s sur­face with clean water to remove any sand­ing residue. Use a soft cloth or tow­el to dry the sur­face com­plete­ly.
  8. Fin­ish and Pol­ish: After wet sand­ing, you may choose to fur­ther enhance the boat’s appear­ance by apply­ing a pol­ish or wax. Fol­low the man­u­fac­tur­er’s instruc­tions for the spe­cif­ic prod­uct you are using.

Rinse the boat reg­u­lar­ly to remove any dust and debris cre­at­ed from the sand­ing process. Once the sur­face is smooth, wipe it with a clean, damp cloth and apply a wax or paint as desired.

When sand­ing, use a light touch and avoid apply­ing too much pres­sure to the boat’s sur­face, as this can dam­age the fiber­glass. It is also impor­tant to sand with the grain of the fiber­glass and not against it. As you work, inspect the boat’s sur­face reg­u­lar­ly to ensure you are remov­ing any blem­ish­es or imper­fec­tions. When done sand­ing, use a clean cloth and a mild deter­gent to remove any residue from the boat’s sur­face. Let the boat dry com­plete­ly before apply­ing wax or paint.

Preparing the Boat for Wet Sanding

Before begin­ning the wet sand­ing process, you need to pre­pare the boat for the job. This includes remov­ing any hard­ware from the boat, such as cleats and rail­ings, and cov­er­ing any areas that should not be sand­ed. You should also thor­ough­ly clean the boat to remove any dirt, dust, and oth­er con­t­a­m­i­nants. If nec­es­sary think of using best boat buffers.

Removing Hardware

The first step in prepar­ing the boat for wet sand­ing is to remove any hard­ware that is attached to the sur­face. This includes items such as cleats, rail­ings, and bimin­is. You should also remove any stick­ers or decals that are on the sur­face of the boat.

Covering Areas

Once all the hard­ware has been removed, you need to cov­er any areas that should not be sand­ed. This includes areas such as win­dows, vents, and any exposed wiring. You can use mask­ing tape and plas­tic sheet­ing to cov­er the areas.

Cleaning the Boat

Before wet sand­ing, you should thor­ough­ly clean the boat to remove any dirt, dust, and oth­er con­t­a­m­i­nants. You can use a pres­sure wash­er or a sponge and warm water to clean the boat. Make sure to rinse the boat thor­ough­ly to remove any soap residue. To check if its done cor­rect­ly see our arti­cle on how to clean an alu­minum boat.

Preparing the Boat for Wet Sanding

Gathering Materials for Wet Sanding

Once the boat is pre­pared for wet sand­ing, you need to gath­er the mate­ri­als and tools nec­es­sary for the job. This includes mate­ri­als such as wet sand­pa­per, a hose, a buck­et, and a sponge.

  • Sand­pa­per: Choose sand­pa­per specif­i­cal­ly designed for wet sand­ing, as it is more durable and effec­tive when used with water. Select a range of grits depend­ing on the lev­el of imper­fec­tions you need to address and the desired smooth­ness of the fin­ish. Com­mon grits for wet sand­ing fiber­glass boats range from 320 to 2000.
  • Sand­ing Block or Pad: These tools pro­vide a sta­ble sur­face for sand­ing and help dis­trib­ute pres­sure even­ly. Opt for a sand­ing block or pad that is com­fort­able to hold and fits well in your hand. Ensure it has a firm and flat sur­face to achieve con­sis­tent results.
  • Water Source: You will need a sup­ply of water to wet the sand­pa­per and keep the sur­face of the boat lubri­cat­ed dur­ing the sand­ing process. A spray bot­tle, hose with a mist­ing noz­zle, or a buck­et of water can be used to wet the sur­face as need­ed.
  • Clean­ing Solu­tion: Before wet sand­ing, it’s essen­tial to thor­ough­ly clean the boat’s sur­face to remove any dirt, grime, or debris. Use a mild deter­gent or boat-spe­cif­ic clean­ing solu­tion and a sponge or soft brush to clean the sur­face. Rinse the boat with water and allow it to dry com­plete­ly before pro­ceed­ing with wet sand­ing.
  • Safe­ty Equip­ment: Pro­tect your­self dur­ing the sand­ing process by wear­ing safe­ty gog­gles or glass­es to shield your eyes from fly­ing debris. Addi­tion­al­ly, con­sid­er using a dust mask or res­pi­ra­tor to pre­vent inhala­tion of dust par­ti­cles.
  • Option­al: Depend­ing on the con­di­tion of the boat and your spe­cif­ic needs, you may also want to have a com­pound or pol­ish to use after wet sand­ing to fur­ther refine and restore the boat’s fin­ish.

To wet sand a fiber­glass boat, you will need a buck­et of clean water, a sponge, sand­pa­per, a sand­ing block, and a pol­ish­ing com­pound. Be sure to choose sand­pa­per with a grit size appro­pri­ate for the job. You may also need a res­pi­ra­tor, safe­ty glass­es, and rub­ber gloves. Start by wet­ting the area with the sponge and water, then use the sand­pa­per and block to sand the area. Apply the pol­ish­ing com­pound and buff to a shine.

You will also need a soft cloth or tow­el to wipe away excess residue. Keep the sur­face wet and use cir­cu­lar motions to avoid scratch­ing. Be sure to sand in one direc­tion rather than back and forth. Take breaks often so that your arms do not become too tired. When you are fin­ished, rinse the area with clean water and dry it with a soft cloth. Fol­low­ing these steps will ensure a smooth, even fin­ish.

Wet Sandpaper

Wet sand­pa­per is the most impor­tant mate­r­i­al for wet sand­ing a fiber­glass boat. The type of sand­pa­per you use will depend on the sever­i­ty of the sur­face imper­fec­tions. You should choose a grit that is coarse enough to remove the imper­fec­tions, but not so coarse that it dam­ages the gel coat.


You will need a hose to keep the sand­pa­per wet while sand­ing. This will help pre­vent the sand­pa­per from clog­ging and ensure that the sand­ing process is as effec­tive as pos­si­ble.


A buck­et is nec­es­sary to store the water that is used to keep the sand­pa­per wet. The water should be changed fre­quent­ly to ensure that it is clean and free of debris.


A sponge can be used to clean the boat after sand­ing. It can also be used to clean the wet sand­pa­per to remove any dirt or debris.

Wet Sanding the Boat

Wet Sanding the Boat

Once you have gath­ered all of the nec­es­sary mate­ri­als, you can begin the wet sand­ing process. This includes wet­ting the sand­pa­per, sand­ing the boat, and rins­ing the boat.

Wetting the Sandpaper

The first step in wet sand­ing is to wet the sand­pa­per. This can be done by sub­merg­ing the sand­pa­per in the buck­et of water or by spray­ing the sand­pa­per with the hose.

Sanding the Boat

Once the sand­pa­per is wet, you can begin sand­ing the boat. Start with a coarse grit and move to a fin­er grit to remove any sur­face imper­fec­tions. Make sure to keep the sand­pa­per wet while sand­ing.

Rinsing the Boat

Once you have fin­ished sand­ing the boat, you should rinse it with the hose to remove any dust or debris. Make sure to rinse the boat thor­ough­ly to ensure that all the dirt and debris have been removed.

Finishing the Sanding Process

Finishing the Sanding Process

Once the boat has been rinsed, you can fin­ish the sand­ing process. This includes clean­ing the boat and check­ing for any remain­ing imper­fec­tions.

Cleaning the Boat

Once the sand­ing is com­plete, you should use a sponge and warm water to clean the boat. This will remove any remain­ing dust or debris.

Checking for Imperfections

Once the boat is clean, you should check for any remain­ing imper­fec­tions. If there are any, you may need to re-sand the area.


How often should I wet sand my fiberglass boat?

It depends on the con­di­tion of your boat’s sur­face and the lev­el of imper­fec­tions you want to address. Wet sand­ing is typ­i­cal­ly per­formed as part of a larg­er boat main­te­nance or restora­tion project. If you notice sig­nif­i­cant scratch­es, oxi­da­tion, or oth­er imper­fec­tions, wet sand­ing can be done as need­ed to restore the smooth­ness and appear­ance of the fiber­glass.

What grit sandpaper should I use for wet sanding a fiberglass boat?

The choice of grit depends on the spe­cif­ic needs of your boat’s sur­face. For remov­ing deep­er scratch­es or imper­fec­tions, you may start with a low­er grit such as 320 or 400. As you progress to fin­er sand­ing and pol­ish­ing, you can switch to high­er grits like 800, 1000, or even up to 2000. It’s impor­tant to start with a coars­er grit and grad­u­al­ly move to fin­er grits to avoid remov­ing too much mate­r­i­al too quick­ly.

Can I wet sand a fiberglass boat by hand?

Yes, wet sand­ing can be done by hand using a sand­ing block or sand­ing pad. This method allows you to have bet­ter con­trol and even pres­sure while sand­ing. How­ev­er, for larg­er areas or if you pre­fer more effi­cient sand­ing, you can also use a machine pol­ish­er or buffer with a suit­able sand­ing attach­ment. Be sure to fol­low the man­u­fac­tur­er’s instruc­tions and exer­cise cau­tion to pre­vent dam­age to the fiber­glass sur­face.


Wet sand­ing is an impor­tant part of the boat restora­tion process. It removes old paint and gel coat, as well as any sur­face imper­fec­tions, to help you achieve a smooth and even fin­ish. This arti­cle pro­vid­ed a step-by-step guide on how to wet sand a fiber­glass boat, includ­ing how to pre­pare the boat, gath­er mate­ri­als, and com­plete the sand­ing process.

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