This years service and upgrading-fuel tank leaks (trawlerfans)

Former owner Randal had problems with leaks from the fueltanks. Gaskets were replaced by a dedicated company in London 2013.
When being together in Cartagena 2017 we cleaned the cruisetank and when lifting the lid saw that the rubbergaskets had deteriorated and were breaking apart.
Having my own share of leakproblems from the fueltanks I decided to change all gaskets again.
The yard in Estonia recommended a gasket material unknown to me (see picture) and all gaskets including devices/gaskets for the gauges were changed. Now being onboard working for a week I pressuretested all tanks by levelling fuel between the tanks with the Walbropump.
Tank 3 and 4 were still leaking but not from the gaskets or gauges as expected but from 1 bolt on each tank !? (see picture).
We found out that the fueltankbolts are not welded but threaded and probably it´s leaking through the threads. I know there are other DD owners having problems with fueltankleaks and if the source is unknown the bolts could be worth looking at.
We will extract the bolts,clean and seal with fuelresistant sealingcompound.

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