# 1278688 Mercury MerCruiser Washer | Genuine Quicksilver OEM Part

🔧 Product Description

  

Genuine Quicksilver Upper Mount Bolt Washer - Part Number: 12-78688

A genuine Quicksilver washer used in Mercury and Mariner V6 swivel bracket and steering arm assemblies. This washer is used in the upper mount bolt hardware stack alongside related mounting components and is used on many V6 outboards where the diagram specifies 12-78688.

  

⚙️ Key Features

  

• Genuine Quicksilver OEM washer

• Correct Mercury part number 12-78688

• Used as an upper mount bolt washer

• Replaces / relates to earlier washer 12-814432 in supported assemblies

• Commonly used in pairs in Mercury / Mariner V6 swivel bracket hardware

  

🔄 Supersession & Cross Reference

  

OEM Supersession Chain:

• 12-78688 → Replaces / supersedes 12-814432 where specified

• 12-814432 earlier upper mount washer reference

OEM / Related Numbers:

• 12-78688

• 78688

• 1278688

• 12-814432

• 814432

• 12-66921 related upper mount bolt washer

• 10-8M0000491 related upper mount screw

• 77326 related upper mount

• 12-816432 related thrust washer

Aftermarket / Verified Equivalents:

• No aftermarket equivalent

  

🚤 Compatibility

  

Commonly used on:

• Mercury / Mariner V6 swivel bracket and steering arm assemblies

• Mercury / Mariner upper mount bolt hardware

• Performance and high-output Mercury outboard mounting assemblies where 12-78688 is specified

Typically suits:

• Engine models:

• Mercury V-150 Work - serial 4868998 to 0A904645

• Mercury V-150 - serial 4868998 to 0A904645

• Mercury V-150 Magnum - serial 5600162 to 0A904645

• Mercury V-150 Marathon - serial 5600162 to 0A904645

• Mercury V-150 XR-2 - serial 4868998 to 0A904645

• Mercury V-150 EFI - serial 0G303046 to 0G760299

• Mercury V-150 EFI - serial 0G760300 to 0G960499

• Mercury V-150 EFI - serial 0G960500 to 0T408999

• Mercury V-150 EFI 2.5L - serial 0T409000 to 0T800999

• Mercury V-150 EFI 2.5L - serial 0T801000 to 1B226999

• Mercury V-150 EFI 2.5L - serial 1B227000 and up

• Mercury V-150 DFI 2.5L - serial 0G590000 to 0G760299

• Mercury V-150 DFI 2.5L - serial 0G760300 to 0G960499

• Mercury V-150 DFI 2.5L - serial 0G960500 to 0T178499

• Mercury V-150 DFI 2.5L - serial 0T178500 to 0T800999

• Mercury V-150 DFI 2.5L - serial 0T801000 to 1B226999

• Mercury V-150 DFI 2.5L - serial 1B227000 to 1B417701

• Mercury V-150 DFI 2.5L - serial 1B417702 and up

• Mercury V-175 - serial 4301235 to 0C100860

• Mercury V-175 - serial 0C100861 to 0C239552

• Mercury V-175 - serial 0C239553 to 0D081999

• Mercury V-175 - serial 0D082000 to 0G303045

• Mercury V-175 - serial 0G303046 to 0G760299

• Mercury V-175 - serial 0G760300 to 0G960499

• Mercury V-175 EFI - serial 0G303046 to 0G760299

• Mercury V-175 EFI - serial 0G760300 to 0G960499

• Mercury V-175 EFI - serial 0G960500 to 0T408999

• Mercury V-175 DFI 2.5L - serial 0T178500 to 0T800999

• Mercury V-175 DFI 2.5L - serial 0T801000 to 1B226999

• Mercury V-175 DFI 2.5L - serial 1B227000 to 1B417701

• Mercury V-175 DFI 2.5L - serial 1B417702 and up

• Mercury V-200 - serial 5624878 to 0C100860

• Mercury V-200 - serial 0C100861 to 0C291519

• Mercury V-200 - serial 0D082000 to 0G303045

• Mercury V-200 - serial 0G303046 to 0G760299

• Mercury V-200 - serial 0G760300 to 0G960499

• Mercury V-200 - serial 0G960500 to 1B226999

• Mercury V-200 EFI - serial 0G303046 to 0G760299

• Mercury V-200 EFI - serial 0G760300 to 0G960499

• Mercury V-200 EFI - serial 0G960500 to 0T408999

• Mercury V-200 EFI 2.5L - serial 0T409000 to 0T800999

• Mercury V-200 EFI 2.5L - serial 0T801000 to 1B226999

• Mercury V-200 EFI 2.5L - serial 1B227000 and up

• Mercury XR-6 - serial 0G303046 to 0G760299

• Mercury XR-6 - serial 0G760300 to 0G960499

• Mercury XR-6 - serial 0G960500 to 1B226999

• Mercury 150 EFI Pro Max / Super Mag - serial 0D935000 to 0G610049

• Mercury 200XS DFI 2.5L - serial 1E000797 to 1E002110

• Mercury 200 EFI Pro Max / Super Mag - serial 0D935000 to 0G610079

• Mercury 225 EFI Pro Max / Super Mag - serial 0D935638 to 0G610103

• Mercury 225X EFI Pro Max - serial 0T430254 to 0T819605

• Mercury 225 EFI Pro Max / Super Mag - serial 0G610104 to 0G856999

• Mercury V-225 - serial 5628028 and up

• Mercury 250 / 275 - serial 0C101891 and up

• Mercury 300 3.4L - serial 5611648 and up

• HP Range: commonly 150HP - 300HP V6 and performance outboard swivel bracket applications where specified

• Engine Type: Mercury / Mariner V6 and high-performance outboard mounting hardware

• System Type: Swivel bracket / steering arm upper mount bolt washer

  

🔌 Function

  

This washer forms part of the upper mount bolt hardware stack and helps spread load, maintain spacing and secure the swivel bracket / steering arm assembly correctly.

Common signs of failure:

• Washer missing during upper mount service

• Upper mount bolt hardware loose or incorrectly stacked

• Washer corroded, distorted or worn

• Excessive movement at upper mount area

• Replacement required during swivel bracket or steering arm repairs

  

📦 Condition

  

• Genuine Quicksilver part

• Brand new

• Supplied in original or equivalent packaging

## Details

- **Price:** 5.05 AUD
- **Vendor:** Quicksilver
- **Tags:** Quicksilver Marine Parts | Oils Service Kits & Engine Components

## Variants

| Variant | Price | Available |
|---------|-------|-----------|
| Default Title | 5.05 AUD | In stock |

## Images

- 1278688 Mercury MerCruiser Washer | Genuine Quicksilver OEM Part

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> Source: [Sawley's Auto and Marine](www.sawleysautoandmarine.com.au/products/1278688-mercury-mercruiser-washer-genuine-quicksilver-oem-part)
> Updated: 2026-05-17