I use that PAC-200 and have never had a problem starting the boat. Note, I have discharged my stereo battery multiple times to the point where i would turn the stereo on and it would turn off almost instantly because it had been depleted. Also, I also have subpar batteries which will be replaced if/when they die. They are going on a little over 3 years. I take them out and condition them in the winter so i am sure that helps. A little bit of insurance would be a take along jump starter, they are cheap enough and are very handy.
In the event that my boat does not start because the stereo battery pulls down the other battery I can just unhook the stereo battery and have full starting juice.