Blisters

Hello everyone,

I have a '86 2001. I have noticed on the hull are these blister like bumps. Not to many about 6 or 7 about the size of a dime.

They are either at or below the water line. Any ideas where they come from and more importantly, how to fix them?

The boat was only in the water since July.

Is this some type of inboard boat STD?

Never leave a boat in the water for more than a few days at a time...unless you have bottom paint applied.

All boats seem to act to this problem differently, I believe it has a lot to do with the porosity(sp) of the gelcoat and the rate at which the surface allows water to be absorbed. I had 2 inboards (MC's)that spent the whole summer in the water without bottom paint. One lasted 5 summers without a blister and the other blistered after one season.

It's called "osmosis". Older fibregla$$ boats all suffer from it to some extent if left in the water and some even in places that stay damp. Modern resins tend to be far more resistant to it, but I'm not sure that those resins are used on ski boats as they aren't, in general, left in the water.

It's caused by water penetrating the layup and reacting with chemicals in the resin, the blisters are caused by the reaction between the water and the chemicals. Fresh water is worse than salt, according to the tech man from International Paints because it's "thinner" and therefore osmoses more easily.

Treatment is by either grinding out the blisters and allowing to dry and then filling with epoxy filler, for minor cases, and for major attacks removing the gelcoat, drying, filling and then coating up with a suitable epoxy paint.

There you go, a bit techy, but understandable I hope.

Oh, and it's an expensive, dirty and labour intensive job.

I suppose eventually they could start to reduce the hull integrity, but they tend to be on the surface of the layup and froce the gel off so they aren't really structural as such.

priority depends on how bad it is and how concerned you are about the look of the bottom of your boat. I guess on a planing craft they will hinder performance to a degree.

People tend to think of osmosis treatment as a professional only job, but there's no mystery to it. You need to dry the hull properly so you need a moisture meter to check it. Then you need a warm dry place to fill it and paint it. Time is the major factor for the DIYer rather then skill.