No, the motor generates it's own ignition spark. How do you think the pull start motors run? A bad ground would probably damage the alternator/charting system.
Also, even if it's an aluminum boat, the hull should never be used as a ground.
2015 Seaark 1872 MV CC Etec-90
Helix 12 CHIRP SI, HB 1199, MinnKota Riptide ST80/i-pilot Link, Bob's Hydraulic
Bitter Gun Owner