Stop and look at your question here. That's about the same as asking "How do I start my coffee maker ?" Without knowing the make and model of your pump, how can we tell your anything ? We don't know the year of your Pearson. Even knowing that, it's not unusual to find more than one make of pump was installed in any particular year. And finally, is this the original pump supplied by the boat manufacturer or something replaced by the previous owner ?
Given the make and model of the pump, nothing could be easier than to locate the owner's manual and a trouble shooting guide. Give us the make and model of the pump and you'll very likely find someone here who has that exact same pump on their Cat or Bene or whatever and has previously dealt with your problem.
Knowing absolutely nothing about your pump, I'll take a wild guess and say it's either the intake or discharge check valve that's failed. And that information along with $2.00 will get you a cup of coffee in most any restaurant.
You help us and we'll help you.