Mercury MerCruiser Lower Swivel Pin | 8M0073409

Mercury MerCruiser Lower Swivel Pin | Part 8M0073409

Part Number: 8M0073409
Full Part Reference: 17-8M0073409
Brand: Mercury Marine / Quicksilver
Official Product Type: Swivel Pin — Lower
Category: Sterndrive Hardware & Fasteners

What It Does

The lower swivel pin is a structural pivot component in the MerCruiser sterndrive tilt and swivel assembly. It passes through the swivel bracket and transom assembly to allow the drive unit to pivot for steering and trim. This pin carries significant load during operation and must be in good condition to maintain proper drive alignment, steering response, and tilt function. A worn, corroded, or bent swivel pin can cause play in the drive, imprecise steering, or binding during trim operation.

System

MerCruiser sterndrive tilt/swivel and transom assembly. The lower swivel pin is part of the swivel bracket system that connects the drive unit to the transom plate, allowing the drive to pivot both for steering (side-to-side) and trim (up-and-down). It works in conjunction with the upper swivel pin, swivel bracket bushings, and related hardware.

Compatible Applications

Always verify fit using your drive model number and serial number against the current Mercury parts diagram. Swivel pin dimensions and specifications can vary between drive generations and production ranges.

• MerCruiser Alpha One sterndrive — confirm by serial number range
• MerCruiser Bravo series sterndrives — confirm by model and serial number
• MerCruiser transom assemblies using part reference 17-8M0073409 in the parts diagram

Serial Requirements

Swivel pin specifications (diameter, length, and finish) can vary between MerCruiser drive generations and production date ranges. Always locate your drive's model number and serial number (on the drive unit data plate) and cross-reference part number 17-8M0073409 in the current Mercury parts diagram before ordering. Do not order by appearance alone.

Dimensions

Exact dimensions vary by application. Confirm against the Mercury parts diagram for your specific drive model and serial number. Do not substitute based on visual similarity — pin diameter and length tolerances are critical for proper fit and load bearing.

Related Parts

Typically inspected or replaced at the same time as the lower swivel pin:

• Mercury MerCruiser Quicksilver Bravo 3 Lower Unit Gear Housing Complete 8M0046738
• Mercury – Upper Gearcase Seal Kit – 26-32511A1 — inspect seals when servicing swivel assembly
• Mercury Mariner Lower Unit Gear Housing Seal Kit – 26-43035A4
• Mercury MerCruiser Quicksilver Bravo Lower Gear Case Seal Kit 76868A04
• Mercury MerCruiser Quicksilver Gear Housing Seal Kit 816575A3

Service Interval

Inspect the lower swivel pin annually or whenever the drive is removed from the transom. Replace if there is visible corrosion, pitting, bending, or measurable wear beyond manufacturer tolerances. Do not reuse a pin that shows signs of galling or deformation. Lubricate the pin and swivel bracket bushings with the appropriate marine grease at each annual service.

Installation Notes

• Clean the swivel bracket bore and inspect bushings before installing the new pin — worn bushings will cause premature pin wear even with a new pin installed
• Apply marine-grade corrosion-resistant grease to the pin before installation
• Follow the Mercury service manual for correct installation direction, retaining hardware torque, and cotter pin or clip requirements
• Inspect the transom plate and swivel bracket for cracks or corrosion damage while the pin is removed
• Do not use anti-seize compounds unless specified by the service manual — some pin installations require specific lubrication types

Technical FAQ

How do I know if my lower swivel pin needs replacement?
Signs include excessive play or slop in the drive unit when pushed side-to-side, binding or stiffness during trim operation, visible corrosion or pitting on the pin, or difficulty removing the pin during service. Any measurable wear beyond the service manual tolerance requires replacement.

Can I reuse the old pin if it looks okay?
Only if it measures within the service manual's wear limits and shows no corrosion, bending, or surface damage. When in doubt, replace it — the cost of a new pin is far less than the consequences of a failed swivel assembly on the water.

Do I need to replace the bushings at the same time?
Yes, in most cases. If the pin shows wear, the bushings are almost certainly worn as well. Installing a new pin into worn bushings will accelerate wear on the new pin and will not restore proper drive alignment.

Is this the same as the upper swivel pin?
No. The upper and lower swivel pins are separate parts with different dimensions. Confirm you are ordering the correct position (lower) for your application using the parts diagram.

Parts Desk Insights

Best use case: Annual sterndrive service or any time the drive is removed from the transom for maintenance. This is also the correct part when diagnosing excessive drive play, steering slop, or trim binding on MerCruiser sterndrive boats. Shops performing full transom assembly rebuilds should stock both upper and lower swivel pins along with the swivel bracket bushing set.

Common mistakes:

• Ordering without confirming the serial number range — swivel pin dimensions vary between drive generations. A pin that looks identical may have a different diameter or length. Always verify against the parts diagram for the specific drive serial number.
• Replacing the pin without replacing the bushings — worn bushings will destroy a new pin quickly. Always inspect and replace bushings as a set.
• Confusing upper and lower swivel pins — they are different parts. Confirm the diagram position (lower) before ordering.
• Skipping lubrication — the swivel pin and bushings must be properly greased at installation and at each annual service. Dry pins corrode and seize rapidly in a marine environment.
• Not inspecting the swivel bracket — a cracked or corroded bracket will cause the new pin to fail prematurely. Inspect the full assembly while the pin is out.