Bad, bad sounds from Bootsy! Might be tough to get exactly that with a single-output instrument. I agree with previous posters that he probably had some OD/light fuzz, but maybe on only some of the outputs from his quad-output Star Bass. Also agree with the slight delay. Lastly, he might be using two EFs in series, which I've read he would do, with one going up and the other going down. (Or if not in series, then on two different outputs of the Star bass.) The dual filters can greatly enhance resonance peak effects like he's getting on this clip.
The Aguilar Filter Twin does this in one box with two filters sweeping in opposite directions, and if I am not mistaken the EHX Bassballs also does this? But Bootsy used two separate pedals, probably MuTron III's.
