Yes, every boat should have one pump onboard, regardless of how many SHOCKWAVE S5 Sentinels are installed. You will need the pump to adjust the pressure at set-up, and the pump will need to be used if an occupant much heavier or lighter than the primary occupant (more than a 50lbs difference) is using it. Also, the pressure should be checked every year and the S5 Sentinel may need to be adjusted slightly.