No yacht has sunk from Osmosis, not that I am aware of anyway, but big blisters will weaken the laminate.
The water and the contaminants in the laminate have to be removed and whilst drying will remove the water it leaves many of the contaminants behind so for this reason steam cleaning and washing the hull surface is important but not sufficient. Depending on how big and how many blisters you have, the decision on how much work is down to you. A few isolated blisters can be carefully cut off with a chisel, washed out and filled with epoxy resin. Even large blisters can be treated this way.
Peeling the gel coat is common but extreme and on its own often adds to problems. Blisters will return, even after peeling, if there are still voids in the laminates and uncured gel coat, more blisters will occur. So if you are the owner and don’t intend to sell, my personal view is deal with them individually as they occur. If you are planning to sell, yes the fact is, boats with untreated osmosis are harder to sell, so you will need to get a professional, warranted job done.
The gel coat is a very effective water barrier and does not allow the passage of glycols so it has to be removed usually by the use of a “Gel Peeler”. This removes a controlled thickness of gel coat/laminate leaving an even surface.
To promote drying and to abrade the surface left by the “Gel Peeler” the peeled surface should be “grit blasted” after peeling, for maximum effect this work should be done immediately after the end of the season. Thereafter the hull should be steam cleaned and washed regularly for a period of time to ensure that the solutions are washed out. At this stage, I would recommend HOTVAC treatment. This cures the uncured resin and reduces he chance of re-occurrence. When the surface is found to be neutral, the drying process can commence. Initially this can be air dried but eventually the hull will need to be heated to reduce moisture content to a very low level. Once the hull is dry a new coating can be applied.
