# 99021A16 Mercury Trigger | Genuine Used Part

🔧 Product Description

  

Genuine Used Mercury Mariner Three-Cylinder Trigger Assembly - Part Number: 99021A16

  

A genuine pre-owned Mercury and Mariner trigger assembly for selected three-cylinder 45 Jet and 50HP through 90HP two-stroke engines.

  

Part number 99021A16 belongs to the three-cylinder 99021 trigger family and is mounted beneath the flywheel to generate ignition-timing signals while moving with the mechanical spark-advance linkage.

  

⚙️ Key Features

  

• Genuine Mercury or Mariner used trigger

• Correct OEM reference 99021A16

• Three-cylinder ignition configuration

• Used on selected 45 Jet and 50HP through 90HP engines

• Mechanical spark-advance assembly

• CDI and Sierra replacements available

  

🔄 Supersession & Cross Reference

  

OEM Supersession / Related Chain:

  

• 99021A3 - Earlier trigger reference

• 99021A5 - Earlier trigger reference

• 99021A7 - Related trigger reference

• 99021A8 - Related trigger reference

• 99021A13 - Later trigger reference

• 99021A15 - Related trigger reference

• 99021A16 - Later service assembly

  

OEM / Related Numbers:

  

• 99021A16

• 99021A3

• 99021A5

• 99021A7

• 99021A8

• 99021A13

• 99021A15

• Trigger Type: Three-Cylinder

  

Aftermarket / Verified Equivalents:

  

• CDI Electronics: 134-9021-3

• Sierra: 18-99393

• Aftermarket trigger replacing the listed 99021A-series references

  

🚤 Compatibility

  

Commonly used on selected:

  

• Mercury 45 Jet

• Mercury 50HP three-cylinder

• Mercury 55HP three-cylinder

• Mercury 60HP three-cylinder

• Mercury 65 Jet

• Mercury 70HP

• Mercury 75HP

• Mercury 80HP

• Mercury 90HP

• Compatible Mariner three-cylinder engines

  

Representative application period:

  

• Approximately 1987-1999, horsepower and serial-number dependent

  

Verified catalogue examples include:

  

• Mercury 50HP three-cylinder 0D000750 through 0G290584

• Mercury 55HP three-cylinder 0D000750 through later 0G-series ranges

• Mercury 60HP three-cylinder 0G290585 through 0G589999

• International three-cylinder 50HP, 55HP and 60HP applications using 99021A16

  

Important fitment note:

  

• Confirm the engine has three cylinders.

• Similar 40HP, 50HP and 60HP Mercury engines may use a different trigger according to cylinder count and ignition system.

• Compare wire colours, connector and advance-arm shape.

  

🔌 Function

  

The trigger produces three crankshaft-position pulses for the ignition switchbox.

  

Its rotational movement advances ignition timing as the throttle is opened.

  

Common signs of failure:

  

• No spark on one or more cylinders

• Intermittent spark

• Spark disappears when warm

• Difficult starting

• Engine backfires

• Misfire during acceleration

• Engine will not reach full rpm

• Trigger wires are cracked or pinched

• Timing does not advance correctly

• Trigger resistance or peak output is outside specification

  

Recommended checks before installation:

  

• Confirm 99021A16 or a listed cross-reference

• Verify the three-cylinder configuration

• Test resistance and peak output

• Inspect the switchbox, stator and coils

• Check the flywheel key and magnets

• Confirm free trigger movement

• Route wiring clear of the flywheel

• Set ignition timing after installation

  

📦 Condition

  

• Genuine Mercury or Mariner used part

• Pre-owned electrical component

• Wire ageing, marks and oxidation may be present

• Electrical testing before installation is strongly recommended

• Included linkage and hardware are limited to those shown or described

• Supplied in protective or equivalent packaging

## Details

- **Price:** 40.0 AUD
- **Vendor:** Sawley's Auto and Marine
- **Tags:** Sawley’s AAM Used Parts – Triggers | Ignition Triggers & Pickup Coils

## Variants

| Variant | Price | Available |
|---------|-------|-----------|
| Default Title | 40.00 AUD | In stock |

## Images

- 99021A16 Mercury Trigger | Genuine Used Part

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> Source: [Sawley's Auto and Marine](https://www.sawleysautoandmarine.com.au/products/99021a16-mercury-trigger-genuine-used-part)
> Updated: 2026-07-12