I have pulled a number of black fuel tanks off of Gemini
Catamarans and cleaned them. No evidence of tanks doing this. If they were chards, and you could see them,the the cleaning
from the drilling was not good to begin with perhaps. I would let those bits dry and try to see if they are made of the same material as the tank. Perhaps they went into the pickup hoses and into the filter and took a while to get to the filter. It is possible that the hoses for the fuel are failing. And if you pulled them off, it is possible that that hose inner wall, for a small area near the crimp came loose and perhaps that is what you are seeing. Can you determine if this is dried bits of hose? It sounds like you might want to remove the tanks again and clean them. The biggest issue we have had is that tanks that are flat bottomed, will accumulate a very thin layer of water
, dirt, and sluge that will not come out until you pull the tanks off the boat, tip them over and look at the dregs in a clean bucket. A seperate polishing system that has a pickup going to the bottom of the tanks which i use to pull the fuel out, pushed to the bottom can't get the sluge off. This is pretty clear when you tip the tank and watch the thin layer slowly slide down the bottom. This thin layer on the bottom of sluge, water
, contanimints is what gets strired up right when you need the engine the most, going out an inlet for example. The RPM
drops and things start to go bad. The other thing is that the fuel removed may be bad and have emulsified water and other issues and should be disposed of. I have seen this happen when some fuel is purchased in jerry jugs while cruising in the Bahamas
, puts it in the locker for storage
and 'forgets' about it for a year+ and then goes to use it. Dirt from the fuel, dirty jugs, age and water/growth can then be introduced. This older, perhaps defective fuel, should be disposed of. There are lots of easy ways to give this away and then have good fuel in tanks, but only after they have been pulled and drained, washed out and dried.