Kit Contents:
- 1 Drive Gear Assembly – PA350S
- 1 Idler Gear Assembly – PA351S
- 4 Roller Bearings – PM038
- 4 High Pressure Seals – PM036
- 4 Low Pressure Seals – PM037
- 2 Center Case Gaskets (.016″) – PM007G01
- 3 Center Case Gaskets (.008″) – PM007G02
Why Rebuild Instead of Replace?
NAPCO 3" pumps are built for field serviceability. A PK300S rebuild kit restores the PA300S to factory performance at a fraction of replacement cost. Stainless steel gears maintain corrosion resistance through multiple rebuild cycles. The center case can be accessed and serviced on-site with standard tools — no need to disconnect from piping. Typical rebuild time is 3–5 hours. See our cost analysis comparing rebuild vs. replacement for more details.
When to Rebuild
- Reduced flow output — the PA300S delivers up to 158 GPM at 280 RPM; significant drops indicate worn internals
- Increased vibration or unusual noise during operation
- Visible fluid leakage past seals at the shaft or case joints
- Higher motor amperage draw at the same flow and pressure
- Declining output during routine delivery operations
What's Inside the Kit
The drive and idler gear assemblies (PA350S/PA351S) are factory-matched stainless steel components — always replace both gears together for proper mesh clearance. Four roller bearings (PM038) support both shafts. High-pressure seals (PM036) and low-pressure seals (PM037) prevent leakage at operating pressures up to 100 PSI. Center case gaskets (two .016″ PM007G01, three .008″ PM007G02) seal the case halves. Total kit weight is 34 lb.
Stainless Steel Advantages
The PK300S stainless steel gears are required for corrosive chemicals, food-contact fluids, pharmaceutical ingredients, and applications where iron contamination is unacceptable. Stainless resists oxidation and pitting from acids, caustics, and chloride-containing solutions. The 3" platform provides high-capacity flow for large-volume chemical transfer operations. For food and beverage applications like syrups and oils, see our food processing pump guide. For non-corrosive applications like petroleum, adhesives, or mining, the PK300C ductile iron kit offers the same performance at lower material cost.
Related Resources
Compatible Pump:
PA300S – 3″ Stainless Steel Pump →Alternative Material:
PK300C – 3″ Ductile Iron Kit →Resources:
Field Maintenance Guide →Repair Procedures →