Mercury MerCruiser OEM Gimbal Ring Hinge Pin Retaining Pin 77039 | Early Sterndrive IA IB 120 140 165 888

Mercury MerCruiser OEM Gimbal Ring Hinge Pin Retaining Pin — Part 77039

• Part Number: 77039
• Full Catalog Number: 17-77039
• Brand: Mercury Marine / MerCruiser (Genuine OEM)
• Official Product Type: Gimbal Ring & Bell Housing Hardware — Hinge Pin Retaining Pin
• System: Sterndrive transom assembly — gimbal ring-to-bell-housing hinge pin retention
• Diagram Position: Hinge pin retaining pin (gimbal ring) in early MerCruiser transom / gimbal-ring assembly diagrams
• Supersedes: 35571 / 17-35571 (earlier Mercury retaining pin)
• Approx. Diameter: 1/8 in. / 3.2 mm
• Qty Required: 2 per applicable gimbal-ring assembly (commonly specified in pairs)
• Weight: approx. 0.02 kg

Early MerCruiser transom hardware only. This retaining pin belongs to the early hinge-pin retention system used on pre-Alpha MerCruiser gimbal-ring assemblies. Later Alpha One and Bravo transom assemblies use threaded hinge-pin hardware — do not order 77039 for a drive that uses threaded hinge pins at the gimbal ring.

What It Does

The 77039 is the genuine OEM hinge pin retaining pin used at the gimbal ring on select early MerCruiser sterndrives. It secures the larger gimbal-ring hinge pin in position at the gimbal ring-to-bell-housing pivot, preventing the hinge pin from backing out during operation. Mercury parts diagrams identify 77039 specifically as the hinge pin retaining pin — gimbal ring. On early MerCruiser installations the retaining end is bent after insertion to lock the pin in place. Because this small pin physically retains the larger hinge pin, a bent, corroded, or fatigued retaining pin should not be reused even if it can still be physically inserted.

Compatible Applications

This retaining pin is for early / pre-Alpha MerCruiser gimbal-ring assemblies only. Confirm fitment by drive serial number and the specific Mercury transom / gimbal-ring diagram. Later Alpha One and Bravo drives use different hinge-pin retention hardware.

Early MerCruiser Inline Drives

• MerCruiser IA / IB / IC — 1964: serial 1684188 through 1777798
• MerCruiser IA / IB / IC EZ-Shift — 1965–1966: serial 1776349 through 2065189
• MerCruiser 120 / 140 — 1967–1969: serial 2062141 through 2791956
• MerCruiser 120 / 140 — 1970–1977: serial 2791957 through 4893634
• MerCruiser 160 — 1967–1969: serial 2065190 through 2763441
• MerCruiser 165 — 1970–1977: serial 2763442 through 4890459

Early MerCruiser V6 & Performance Drives

• MerCruiser 225-S — 1974: serial 3856268 through 4200499
• MerCruiser 233 — 1975–1977: serial 4200500 and up
• MerCruiser 888 — 1971–1977: serial 3106717 and up

Not sure it fits? Send us your MerCruiser drive or transom assembly serial number before ordering.

Related Gimbal Ring & Hinge Assembly Components

On applicable early MerCruiser assemblies, 77039 works with the gimbal ring hinge pin and the following related components. These are sold separately and are not included with the retaining pin:

• 77361A1 — Gimbal ring-to-bell-housing hinge pin assembly
• 38031 — Earlier hinge pin reference (applicable early assemblies)
• 77633Q — Gimbal ring grease fitting cap
• 67356A1 — Shock absorber (applicable early assemblies)
• 32607 — Shock absorber-to-gimbal-ring pin (selected configurations)

Part Numbers & Supersession

• 77039 / 17-77039 — Current Mercury Marine OEM reference
• 35571 / 17-35571 — Earlier Mercury retaining pin; superseded by 77039

When to Replace

Replace the hinge pin retaining pin when:

• The pin is bent, distorted, or broken
• Corrosion has visibly weakened the pin body
• The pin is damaged during hinge-pin removal
• The retaining end has been previously over-bent or shows metal fatigue
• The pin is missing from the hinge assembly
• Gimbal-ring service or hinge-pin removal disturbs the retaining pin

Service Interval

Inspect at each gimbal-ring and transom-assembly service and whenever the hinge pin is removed. On early MerCruiser assemblies the retaining pin is a bend-to-retain type — it should not be straightened and reused after removal, as repeated bending fatigues the pin. Always fit a new retaining pin after any hinge-pin removal service. Inspect the hinge pin bore in the gimbal ring for elongation or corrosion at the same time, and replace any corroded or loose hinge-pin hardware before returning the drive to service.

Installation Notes

• Confirm 77039 is the correct retaining pin for your specific drive serial number and early MerCruiser gimbal-ring diagram before installing — later Alpha One and Bravo drives use different hinge-pin retention hardware
• Two retaining pins are commonly required per gimbal-ring assembly — order both if servicing the full hinge-pin assembly
• Inspect the hinge pin (77361A1 or applicable reference) for wear or corrosion before refitting — a worn hinge pin in an elongated bore will not be corrected by a new retaining pin
• Check the gimbal-ring hinge bore for elongation or corrosion at the pivot area
• Inspect the bell-housing pivot area for wear before reassembly
• Follow the applicable MerCruiser service procedure for retaining-pin installation and final retention — on early bend-to-retain designs, bend the retaining end only as specified to avoid over-fatiguing the new pin

Technical FAQ

Q: Does 77039 fit Alpha One or Bravo drives?
No. The 77039 hinge pin retaining pin belongs to the early pre-Alpha MerCruiser gimbal-ring hinge pin system used on IA/IB/IC, 120/140, 160, 165, 225-S, 233, and 888 drives. Later Alpha One and Bravo transom assemblies use threaded hinge pins with different retention hardware. Confirm your drive generation and serial number before ordering.

Q: My parts list shows 35571 — what do I order?
Order 77039 / 17-77039. Mercury superseded 35571 to 77039. The 77039 is the current OEM retaining pin for applicable early MerCruiser gimbal-ring assemblies.

Q: Can I reuse the retaining pin after removing the hinge pin?
No. The early MerCruiser retaining pin is a bend-to-retain type. Once the bent end is straightened for removal, the metal has been fatigued and the pin should not be reused. Always fit a new 77039 after any service that requires removing the hinge pin.

Q: How many retaining pins do I need?
Two retaining pins are commonly specified per gimbal-ring assembly on applicable early MerCruiser drives. Confirm the quantity from the specific Mercury gimbal-ring diagram for your drive serial number before ordering.

Parts Desk Insights

The key thing with 77039 is making sure the customer has the right generation of MerCruiser transom assembly before ordering. This is the small retaining pin for the early bend-to-retain hinge pin system — it has nothing to do with the threaded hinge pins used on Alpha One and Bravo drives. The most common mistake is ordering this for a later drive because the customer knows their drive has a gimbal ring. The other point worth making is that these pins come out bent and should not go back in — they are inexpensive and a new pin should always be fitted after any hinge-pin removal. Remind customers to order two if they are doing both sides of the hinge pin assembly, and to inspect the hinge pin bore in the gimbal ring for elongation while the pin is out.