Disclaimer: Complete "Playing Doctor Achievement" before starting any missions at the beginning of the game in Portland. It will become extremely difficult once gang members become hostile.
This is one of Donald Love mission, who has a "D" icon on the map. It involves taking a boat and picking up some packages for him.
You can reach the boat on the map with any car or boat, you'll still have plenty of time. After getting 6 packages, you get a 5-star chase. I collected 6 packages and headed to the nearest Pain n Spay. You can get rid of the cops at Pain n Spay, even if they're there. Then you can complete the mission.