Volvo Penta HS1A Reverse Gear O-Ring 977890 | Inboard Transmission Seal
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Part Details
- Part Number: 977890
- Brand: Volvo Penta
- Type: O-ring — internal transmission valve/housing seal
- System: HS1A reverse gear / inboard transmission — internal hydraulic and mechanical assembly
- Diagram Position: Internal valve/housing assembly — adjacent to cover 872567 and housing 872525
- Included In: Gasket kit 876588 (HS1A transmission service kit)
- Qty Per Assembly: 1
- Weight: Approx. 0.05 kg
- Important: Replace at every disassembly — do not reuse a compressed or aged transmission O-ring
About This Part
Genuine Volvo Penta 977890 is an OEM O-ring used inside selected Volvo Penta HS1A marine reverse-gear and inboard transmission assemblies. Parts diagrams place 977890 directly beside cover 872567, housing 872525, sealing ring 872701, and related valve components within the transmission’s internal assembly. The HS1A transmission contains several different O-rings in close proximity — confirm the transmission model, ratio, and exact diagram position before ordering, as nearby seals 925058, 955983, 956000, 977891, 925260, and 925263 occupy different positions and are not interchangeable. For major HS1A overhaul work, 977890 is also included in complete gasket kit 876588.
Compatible Applications
- Volvo Penta HS1A — internal valve/housing O-ring position
- Volvo Penta HS1A 1.96:1 — internal valve/housing O-ring position
- Volvo Penta HS1A 2.62:1 — internal valve/housing O-ring position
Confirm transmission model, gear ratio, and exact diagram position before ordering. Several different O-rings are used within the HS1A transmission — position matching from the exploded diagram is essential.
When to Replace
Replace this O-ring whenever the associated transmission cover or internal assembly is opened, and any time the existing seal shows:
- Flattening or permanent compression set
- Hardening or brittleness from age or heat
- Cuts, nicks, or tears
- Swelling or distortion
- Association with transmission-oil leakage at the covered area
For complete HS1A overhaul service, gasket kit 876588 supplies this O-ring along with other seals required for a full rebuild.
Installation Notes
Clean the O-ring groove and mating surfaces thoroughly before installation. Ensure the new seal is seated evenly and is not twisted or pinched during reassembly. Follow the applicable Volvo Penta HS1A workshop procedure for transmission disassembly, internal component adjustment, and final oil-level checks after reassembly.
Related Parts in This Assembly
- Cover: 872567 — adjacent component in the same internal assembly
- Housing: 872525 — adjacent component in the same internal assembly
- Sealing ring: 872701 — sealing component in the same internal valve assembly
- HS1A transmission gasket kit: 876588 — complete seal kit for HS1A overhaul service (includes 977890)
- Related O-rings (different positions): 925058, 955983, 956000, 977891, 925260, 925263 — other seals in the same transmission; confirm positions from diagram
Cross-Reference Part Numbers
- OEM: 977890
- Included in gasket kit: 876588
- Note: No confirmed Volvo Penta OEM superseding number identified in current parts references.
Parts Desk Insight
977890 is specifically tied to the HS1A reverse-gear assembly and should not be treated as a general-purpose Volvo Penta O-ring. The most common ordering mistake is selecting an O-ring by size or appearance rather than diagram position, since several different seals sit close together in the HS1A internal assembly. If a full HS1A overhaul is being performed, ordering gasket kit 876588 rather than individual O-rings is usually more efficient, as it covers the complete set of internal seals required for a thorough rebuild.
Shipping information
In-stock and OEM parts: ship same or next business day.
Supplier-stock items are usually ready for pickup or shipping within 24 hours of ordering.
Special-order timing may vary.
Returns & warranty
Returns & Satisfaction Guarantee
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If you are not fully satisfied, you may request a return within 30 days of delivery. All returns must receive pre-approval prior to being sent back. Unauthorized returns will not be accepted.
To qualify for a return:
Item must be in new, unused condition
Product must be in its original packaging
All parts, components, hardware, manuals, and accessories must be included
Packaging must be undamaged and suitable for resale
Important:
Electronics are strictly inspected. No returns on open-box electronics. Exceptions may apply only with prior written approval. Any electronic unit that has been installed, powered, activated, or altered may not be eligible for return.
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