How do I finish the 'Saving Oliver' mission?

I am playing Far Cry 3 and I am stuck on the Saving Oliver mission after talking to Willis. He keeps running out to fight the pirates and getting killed. Is there a way to make this mission easier? Any help and tips would be appreciated.

The best advice I have is to keep a watchful eye for enemies before they can spot and fire at Oliver. Rather than keeping your rifle's scope on Oliver keep your sights pointed in the direction he's running as that's the way most enemies will approach from.

Additionally, there are barrels scattered around the area. Shoot these red and white barrels and they will explode and take out groups of pirates if you time it right.

Once Oliver safely makes it to the helicopter you'll need to enter a boat. Once inside use the mounted machine gun to fire continuously at any combatants. The gun will not run out of ammunition but may overheat if you hold the trigger too long - I never ran into this issue but it may happen to you. Keep an eye out for explosive barrels again and target those to take out most enemies on the river.

So long as you prioritize accuracy over volume of fire with the rifle and then prioritize volume of fire over accuracy on the boat you should be okay. If necessary, try lowering the difficulty to easy or watch IGN's step-by-step guide of the mission.