If you outnumber the triremes, then you may be able to kill him without loss. Beware shore-based catapults and juggernaughts, though. They're the bane of the galley. Oh yes, one interesting tip. It's one or the other, never both.
Boats are twice as resistant to conversion as other units.
The Fire Galley is a short-range vessel used to defend against other ships. Fire Galleys take additional damage from Ballistas, Helepolises, Stone Throwers, Catapults, Heavy Catapults, Catapult Triremes, and Juggernaughts, whose heavy artillery can shatter the Fire Galley's burning fire pots and set fire to the ship. Ancient mariners devised several ways to set enemy ships on fire. The simplest was to fire flaming arrows or ballista bolts on an enemy ship. Next most useful were flaming grenades, something like modern Molotov cocktails, filled with a combustible liquid like oil.