Re: what the heck is this??
After time, gunk builds up in a boat tank.
They set and condensation forms and collects.
It eventually turns into scale or sludge.
You've got sludge.
Install a water/fuel seperating filter between the tank and the squeezie ball.
Someplace under the rear at the transom.Out of the way and someplace it won't get wet.
Ethanol is alcohol and contains water and is not our friend.It can after a while(quite a while) seperate and the water settle to the bottom.
The best bet is to add ethanol treatment and keep the tank full when not operating.