i put boat down couple days ago i found this brown stuff in racor bowl drain run engine this morning found same stuff i have fibbre tank i have to demolish half boat to get tank out anyone had this problem before i scared to go fish nights or for alongi.
The brown sludge you describe is called diesel bug and is bacteria that grows between the water and the diesel of course with movement of the boat it tends to get stirred up and gets drawn into the Engine.
Sounds like somehow you got water into your diesel, either through a bad seal on the deck filler cap if you have one, or through condensation. You're going to need to flush pump your tank, change your filters as they start to rot etc.
You could try and speak with SD Yachts as they have Clin'Azur and Liquid Engineering range of products for cleaning tanks etc, but you def need to get the fuel tank and lines cleaned.
I would still suggest that once you have everything open that you buy/use one of these specialised cleaning product to eliminate the diesel bug/bacteria that accumulates in the tank and fuel lines and prevent it re-occuring.
Replacing the deck O-ring should be done every year for maximum safety.