Re: Water tank gelcoat

Mark Erdos

Has anyone ever had problems with osmosis occurring from the inside of the boat because of the water tank?


With best regards,





Sailing Vessel - Cream Puff - SM2K - #275

Currently cruising - Tahiti, French Polynesia



On 3/23/2022 11:56 PM, James Alton via wrote:

   The gelcoat in our water tank has some checks in it and is in places flaking away.  In general, if your boat is one of those that is developing blisters elsewhere such as the bottom, then I would consider epoxy sealing the inside of the tank, and yes it would be a pretty horrible job as part or all of the top of the tank would need to be cut away for access!   If your boat is blister free as ours is  I would just do a good clean up on the tank and vacuum out any loose chips, if the laminate were blister prone you would see them by now.  I don't understand the reason for painting the keel bolts/nuts.  Unlike steel, stainless/Inox needs to be exposed to O2 in order to develop the oxide to protect itself.  


James Alton
SV Sueno
Maramu #220

-----Original Message-----
From: Kimberly Bunch via <kimberlybunch@...>
Sent: Thu, Mar 24, 2022 11:05 am
Subject: [AmelYachtOwners] Water tank gelcoat

Good day,

Anyone has any experience and/or advices about the gelcoat cracking inside the water tanks of our Maramu? 
We had to dry the tank in order to treat and paint the keel bolts. Next day, as the paint was drying, the walls of the tanks which had already a few cracks were cracking and flecking in many places. Is it bad? Can it present a risk to the fiberglass now exposed to the water in the tank? Are we going to have osmosis in the tank? 
Sanding the gelcoat where it is flecking seems physically impossible.
Any advice would be greatly appreciated


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