No, one bulb will suffice. What you should do is fill the water separator with fuel/oil mix to prevent the fuel line from giving you a really hard time priming. I also like to take the fuel line free from the fuel pump and pump it up until all the air is out of the line. This will make it much easier to start her up the first time. The bulb should be AFTER the separator and before the outboard.
A trick that I learned was to pump the bulb, kink the hose between the bulb and motor, and release the bulb. Then release the kink, pump the bulb and do it again. This helps to get all the air out of the line. Sometimes priming a fuel line when the tank is below deck can be very difficult.