Introduction8 Ball is going to assist you in blowing up the Cartel Spank ship.
The ActionFirstly you'll need to pay 8 Ball $100,000 to cover the costs, so if you have that money now, pay him it to start the mission. If not, go and do some Taxi missions to earn it. Once you've paid, 8 Ball will give you a Sniper Rifle. You need to do the shooting and keep him safe while he plants the bombs as he can't fire a weapon with his hands. Drive to the Harbor and park in the blue circle. 8 Ball will give you the order to open fire, but first you should make your way onto the roof of the large warehouse to your right. You can get here by going around the building and up the stairs on the corner. Make your way into the corner of the roof, then use your sniper rifle to pick off the two guards at the bottom of the ramp. Start from the back of the ship and snipe all of the Cartel members from left to right, and clear a path for 8 Ball. He'll run in and plant the bomb, then you can watch a cutscene where the ship is blown to bits.
Additional NotesYou can feel free to grab a Cartel Cruiser after the mission, as it's the only chance you'll have of getting one on Portland.