O-Ring | ZF Industries 0634303118

ZF Marine 0634303118 O-Ring | ZF / Hurth Marine Transmission | Replaces Hurth 0634303118, 105530

The ZF Marine #0634303118 is a replacement O-ring for ZF and Hurth marine inboard transmissions. Replaces Hurth 0634303118 and Hurth 105530. Confirm the specific location within your ZF or Hurth transmission that uses this O-ring in your transmission's parts documentation before ordering.

Product Details:

• Part Number: 0634303118 (ZF Marine / ZF Industries)
• SKU: ZF-0634303118
• Manufacturer: ZF Marine
• Type: O-Ring
• Application: ZF / Hurth marine inboard transmission
• Replaces: Hurth 0634303118; Hurth 105530
• Condition: New

Cross-Reference — Replaces:

• Hurth: 0634303118
• Hurth: 105530

Additional Information

ZF / Hurth Marine Transmission — Background:

ZF Marine (formerly ZF Hurth, and before that Hurth Getriebe) manufactures marine inboard transmissions widely used in pleasure craft, commercial vessels, and workboats. Hurth transmissions were rebranded under the ZF Marine name following ZF Friedrichshafen AG's acquisition. Common ZF/Hurth transmission models found in marine applications include the ZF 10, ZF 15, ZF 25, ZF 45, ZF 63, ZF 80, and ZF 85 series, as well as older Hurth HBW and ZF BW series transmissions. These transmissions appear in a wide range of inboard-powered vessels including Chris-Craft, Trojan, Hatteras, Egg Harbor, and other builders that specified ZF/Hurth units from the 1970s through the present.

O-Ring Location — Confirm Before Ordering:

ZF and Hurth marine transmissions use O-rings in multiple locations including oil filter covers, dipstick tube seals, cooler line fittings, drain and fill plug seals, shift linkage seals, and external cover gasket interfaces. The part number 0634303118 / Hurth 105530 identifies a specific O-ring within the transmission — confirm the location in your transmission's parts breakdown or service manual before ordering to ensure this is the correct O-ring for your application. If you need assistance identifying the correct O-ring for your ZF or Hurth transmission, contact us at MacombMarineParts.com with your transmission model number.

O-Ring Replacement — When and Why:

O-rings in marine transmissions are subject to heat cycling, hydraulic fluid exposure, and compression set over time. Replace transmission O-rings when:

• Oil seepage or weeping is visible at the O-ring's location on the transmission housing
• The transmission is being disassembled for service — replace all disturbed O-rings at reassembly as a standard practice
• The O-ring has been removed and is being reinstalled — a previously compressed O-ring may not return to full cross-section and can fail to seal on reinstallation
• The transmission has been in service for an extended period without O-ring replacement — rubber O-rings harden and lose elasticity with age and heat cycling

Installation Notes:

• Confirm this O-ring's specific location in your ZF or Hurth transmission parts documentation before ordering
• Confirm your transmission model number — ZF/Hurth transmission model numbers are typically found on the identification plate on the transmission housing
• Lubricate the new O-ring with clean transmission fluid or petroleum jelly before installation to prevent tearing during assembly
• Do not reuse a previously compressed O-ring — install a new O-ring whenever a seal interface is disturbed
• Inspect the mating surface (groove and bore) for corrosion, scoring, or debris before installing the new O-ring
• Check for seepage at the O-ring location after first run following installation

Frequently Asked Questions

1. What ZF or Hurth transmission models use this O-ring?
Confirm your transmission model uses ZF/Hurth part number 0634303118 or Hurth 105530 in your transmission's parts breakdown. Contact us at MacombMarineParts.com with your transmission model number for assistance.

2. What is the difference between ZF and Hurth?
Hurth Getriebe was a German marine transmission manufacturer acquired by ZF Friedrichshafen AG. Transmissions originally sold under the Hurth name were rebranded as ZF Marine. Many older Hurth transmissions (HBW series, BW series) remain in service, and ZF Marine continues to supply parts under both ZF and Hurth part numbers for these units.

3. Can I reuse the old O-ring if it looks okay?
Not recommended — O-rings compress-set under load and may not return to full cross-section after removal. A reused O-ring risks seeping at the reinstalled interface. Replace whenever the seal location is disturbed.

4. How do I find my ZF/Hurth transmission model number?
The model number and serial number are stamped on an identification plate on the transmission housing. Record both before ordering parts to ensure fitment confirmation.

5. Should I lubricate the O-ring before installation?
Yes — lubricate with clean transmission fluid or petroleum jelly before installing. This prevents tearing the O-ring during assembly and helps it seat evenly in the groove.