3M 5200 Marine Sealant

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3M 5200 is a crucial member of any boater's lineup. 5200 is an adhesive and sealant that is very nearly permanent, flexible, durable, and water tight. It is typically used for thru-hull applications such as sealing around a thru-hull fitting, sealing a hole left by a screw, or as a seal and adhesive for a transom motor bracket.

If you're looking for something a little less permanent for top side work (above the waterline), take a look at 3M 4200 which is still quite permanent and polyurethane based or 3M 3200 which is silicone based and non-bonding. This is IMPORANT. Many people use 5200 when 4200 or 3200 would be more than enough. Remember, 5200 is about as permanent as it gets, it's bonding properties are among the strongest imaginable, and it's very messy to work with. For crucial thru-hull or structural bonding, it can't be beat. However, to seal the screw holes for the light switch on the console will be alright with 3200. You'll save yourself a lot of headache when the switch goes out the next time.

3M provides a great table for selecting between the 3 options,[1] and we are maintaining our own version on Boatpedia called the 3M Marine Sealant Selection Guide. However, at a quick glance main qualities of 5200 are listed below.


  • Sealing
  • Bonding
  • Below water applications
  • Not removable (with out a heat gun, a razor blade, and a ton of determination)
  • Polyurethane based


These are just a few of the common uses of 5200, however, it is used in just about every way imaginable when it comes to sealing or bonding:

  • Deck to hull bonding
  • Sealing above and below waterline
  • General purpose sealing and bonding
  • Keel bonding
  • Bedding
  • Bonding anti-slip plates
  • Bonding thru-hull
  • Bonding wood to wood
  • Bonding fiberglass

Normal vs Fast Cure[edit]

There is no difference in permanence or strength of 5200 vs 5200 Fast Cure. The main difference is just the price. In fact, on 3M's website often times 5200 FC is listed as a best choice where normal 5200 is listed as an okay choice.

5200 and 5200 FC Cure Times
3M 5200 3M 5200 Fast Cure
Curing time 7 Days 24 Hours
Tack-free time 48 Hours 2 Hours

Tips and Tricks[edit]

  • Use paint thinner for clean-up instead of acetone or lacquer thinner
  • Unused 5200 left in the tube can be saved for quite a while. If you have a partial tube, unscrew the plastic applicator and plug up the spout somehow (Electrical tape works well). Put it in the fridge and simply allow it to rewarm for 30 minutes or so when you go to use the rest
  • Best price is usually found at Home Depot. West Marine/similar or Amazon generally sell for $16-17 vs $10 at Home Depot.
  • Have paper towels on hand for the inevitable cleanup around the application area
  • Masking areas you're not sealing or bonding is very helpful and will save a lot of time on cleanup[2]
  • Mix 50-50 dish detergent and water. Once you applied the 5200, dip your finger in the detergent water combo and use your finger, not a putty knife, to smooth out the 5200. No mess and a very smooth finish.[3]
  • Apply less than you think of 5200. You can always apply more. But if you apply too much, then you better have a ton of paper towels handy
  • Latex or purple nitrile gloves help on clean up of your hands[4]


  1. 3M
  2. Wooden Boat
  3. Sailboat Owners
  4. Continuous Wave