Fluid leaking from blisters on hull

If it is a polyester laminate and you have blister and pinholes all over the place, it is undissolved/unreacted MEKP. Once moisture gets in, it reacts with water and an acrid smell and dark tar like substance forms. If it is gel coat deep only, you will have to strip the gel coat.

 

This is a very old boat (at least 30 years), his boat is in a high humidity tropical area that has had incredible rainfall in recent times, does that offer any further insight ?

 

It takes a long time for the water molecules to penetrate the resin/gel coat barrier thru the osmosis process. Hydrolysis is defined as a chemical decomposition of a chemical compound through the reaction with water. A pinhole hastens the process. Pinholes come from trapped micro bubbles.

If it is 30 years old, it must have served its life well and must be of good quality. Some boats takes only 5 years of constant immersion before the blisters starts showing. It is usually poor workmanship or quality of materials. Sometimes equipment. In cases where a gel coat sprayer is used, the mekp and the resin is mixed in the air in a fine mist. If not calibrated properly, the mekp forms droplets and is trapped.

 

As RX mentioned, there are many possible causes of the blistering, and "fixing" them can be time consuming and costly, and unless you do a complete and thorough job, the "fix" may fail again in the near future.

 

Blister is not common only to polyester boats. Epoxy suffers the same but much less degree. If you try to grind away a large patch and it shows the blistering and pinholes are only outer layer deep, then it might be worth it to re seal. If not, I agree with ondarvr, it might not be worth fixing it.

 

Has no odour or taste !

 

Well at the end of the day it will still float however it looks

 

Thanks for the insights my learned brethren, like this site.

 

I can tell you exactly what has happened to your Fiberglass boat hull! I ran the Plastics creation and repair of all craft for 6 years at LaCeiba Shipyard in Honduras.
One of the most frequent repairs of all Fiberglass hulls was BLISTERS!
"Lesson in Polyester Resin". Polyester resin never cures completely unless it is cured under heat and usually vacuum, with a special hardener. When DDM or MEKP hardener is used, as is usually the case, and the hull is sitting in warm water for long periods there is some absorption of water and the uncured particles of the resin tend to expand and raise a blister. Any fluid seen on the outside can usually be wiped away with water but the blister can only be corrected by grinding away the blistered area and sealed with epoxy. Cut small to larger patches with fiberglass and Epoxy until the depression is filled and sanded smooth to the hull shape. I always had sanded the the entire bottom and completed the process by rolling on a coating of Epoxy. Since your hull is completely dry the coating of epoxy will prevent any more water absorption and chance of more blisters! Hope this helps, Russ