Gelcoat Blister Repair: Six Questions

[WeekendWarrior]

I have a 1969 [unidentifed model and length of Boston Whaler] boat that I've owned since 2017. I have been wet-slipping the boat for the past several seasons and noticed that the gelcoat was blistering significantly below the waterline. This winter, I am working on repairing the hull blisters.

I removed the boat interior, and the hull is upside down in the garage. I gave the entire bottom below the waterline an initial sand down the blisters, and to size up what I'm working with.

See photos below.

Q1: What would be the best course of action going forward?

My initial plan was to go down to the fiberglass, epoxy barrier coat, and then new gelcoat. Or I was thinking I could do new gelcoat and then barrier coat and bottom paint below the waterline.

Q12: do I need to [sand] down the [entire] hull to the laminating layers?

Q3: do I only need to sand the areas of the hull where it is really badly pitted from the blistering?

Q4: what is the process for making repairs?

Q5: should a barrier coat be applied?

Q6: should new gelcoat be applied?

This hull has clearly had work done in the past that I'm slowly uncovering as I continue sanding.

I don't believe the hull is waterlogged, as it has no soft spots. I an four friends were was able to pull off the hull from the trailer, flip over the full, and carry the hull into the garage without much effort.

I will very much appreciated any insights.

Fig. 1.

Whaler1.JPG (66 KiB) Viewed 452 times

Fig. 2.

Whaler2.JPG (84.01 KiB) Viewed 452 times

Fig. 3.

Whaler3.JPG (85.34 KiB) Viewed 452 times

[jimh]

Q5: should a barrier coat be applied?

When your restoration is totally finished, a clear barrier coat can be appled to the areas of the hull below the normal waterline, and if marine growth is anticipated an anti-fouling coat applied on top. See the owner’s manual for more advice.

If you do not have the owner’s manual for boat, you can read either of two owner’s manuals thar I have created as HTML documents. From the photographs your boat looks like a17-footer or small, so the appropriate manual will be

https://continuouswave.com/whaler/reference/manual9-17/

Read about barrier coats at

https://continuouswave.com/whaler/refer ... tml#bottom

When asking for advice, give the model year, the model type, and the length of the boat. This information will hep readers to assist you.

[jimh]

Given the extent of the hull rash, a repair that attempted to work only on isolated individual areas would not be a good approach. In addition to blisters the hull has crazing and cracking.

The best method may be to sand the entire hull bottom and sides, removing all the defects.

Areas with deep depressions and pits may need to be filled with epoxy resin mixed with a filler. Then carefully sand the epoxy areas to be flush or fair.

Be very careful when trying to sand fair the cured epoxy resin-filler areas. Your sanding will tend to remove old gel coat resin much faster than hard cured epoxy resin.

Follow on using a fairing compound to fill small depressions .

When the hull bottom is repaired and faired, it will be ready for application of a top coat or two.

If you are skilled in the use and application of the top coat material you plan to use, you could attempt this step yourself.

Using gel coat resin as the new top coat should not be undertaken lightly.

Using exotic marine two-part hull paint can be expensive and difficult.

We are talking about 50-year-old or older small open skiff, so a yacht finish may not really be the goal.

Look at TotalBoat for refinishing paints and materials.

Also watch this recorded presentation:

https://youtu.be/4tZDBOYqdfA?si=e4_ph2l_M0c55WJ7