MERCURY 43-44104T Gearcase Gear Set 1647-9147 1.87 43-44104A T4

( Manufacturer Part Number: 43-44104T ), ( Part Type: Gear )

Review MERCURY Gearcase Gear Set 1.87 Ratio T4

The **Mercury 43-44104T 1647-9147 Gearcase Gear Set (1.87 Ratio, Model 43-44104A/T4)** is a precision-engineered transmission component designed exclusively for high-performance outboard motors, ensuring optimal power transfer and reliability in demanding marine environments. This gear set is a critical part of the outboard s drive system, featuring a **1.87:1 reduction ratio**, which balances torque output with engine efficiency, allowing for smoother acceleration, improved fuel economy, and extended gearcase longevity. Crafted from high-grade, heat-treated steel, the gears are machined to exacting tolerances to minimize wear and vibration, even under heavy loads or prolonged use in rough water conditions. The set includes a **primary drive gear**, **idler gear**, and **output shaft gear**, all meticulously aligned to reduce backlash and ensure seamless engagement with the propeller shaft. Compatible with Mercury s **43-44104A and T4 outboard models**, this gear set is engineered to withstand the stresses of saltwater corrosion, thermal fluctuations, and the constant motion of marine propulsion, making it an essential upgrade for anglers, boaters, and performance enthusiasts seeking enhanced durability and performance. Whether used in stock applications or as part of a custom tuning project, this gear set delivers a noticeable improvement in throttle response and overall drivetrain efficiency, reinforcing the reliability of Mercury s outboard systems. Proper installation requires adherence to factory specifications, including the use of fresh gearcase oil and alignment tools to prevent premature wear or damage. For those maintaining or upgrading their Mercury outboard, this gear set represents a direct investment in performance, longevity, and peace of mind on the water.

### **Pros and Cons of buying a Mercury 43-44104T / 1647-9147 Gearcase Gear Set (1.87 Ratio, Part #43-44104A T4)**

1. **Compatibility with Mercury Outboards** This gear set is specifically designed for Mercury outboard engines, particularly the **T4 series (e.g., 40-50 HP models)** and some older models like the **43-44104T**. It ensures proper gear engagement and smooth operation when installed correctly.

2. **Performance Optimization** The **1.87 gear ratio** is optimized for **faster acceleration and better low-end torque**, making it ideal for **fishing boats, personal watercraft (PWC) conversions, or applications requiring quick response** (e.g., trolling, maneuvering in tight spaces).

3. **Durability & Reliability** Mercury gearcases are built to withstand **heavy loads and frequent use**, especially in marine environments. The **T4 series** is known for its robust construction, reducing the risk of premature wear if properly maintained.

4. **Easier Installation (Compared to Stock Gears)** Some aftermarket gear sets (like this one) are designed to **replace stock gears without major modifications**, making them a **DIY-friendly upgrade** for those comfortable with basic mechanical work.

5. **Potential for Better Fuel Efficiency** A properly matched gear ratio can **reduce strain on the engine**, leading to **slightly improved fuel economy** in certain conditions (e.g., steady cruising speeds).

6. **Availability of Replacement Parts** Since Mercury is a major manufacturer, **replacement gears, seals, and related components** are widely available, reducing long-term maintenance hassles.

7. **Cost-Effective Upgrade** Compared to a **full gearcase overhaul or engine swap**, replacing just the gear set is a **relatively inexpensive performance boost** (typically **$100 $300**, depending on source and condition).

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1. **Potential Compatibility Issues** While this gear set is designed for **T4 series engines**, **exact model matching is critical**. Using it on a **non-T4 engine (e.g., T5, T6, or older models)** could lead to **poor performance, excessive wear, or even damage**. Always verify **engine model, shaft length, and gearcase type** before purchasing.

2. **Risk of Improper Installation** If not installed correctly, **misalignment or incorrect torque settings** can cause **premature gear failure, bearing damage, or even shaft breakage**. Requires **proper tools (torque wrench, alignment guides) and mechanical skill**.

3. **No Direct Performance Guarantee** While the **1.87 ratio is generally faster**, some users report **reduced top-end speed** compared to stock gears (e.g., 2.5:1). If **high-speed cruising** is a priority, this may not be the best choice.

4. **Warranty Void Risk** Installing aftermarket gears **may void the manufacturer s warranty**, especially if not done by an authorized dealer. Mercury s warranty policies can vary, so check before proceeding.

5. **Potential for Increased Wear on Other Components** A **higher gear ratio (1.87) increases engine RPM at a given speed**, which can **stress the transmission, clutch (if applicable), and engine internals** over time if the engine isn t properly tuned or cooled.

6. **Limited Longevity in Rough Conditions** While durable, **constant operation in abrasive environments (e.g., saltwater without proper flushing, debris-heavy water)** can still lead to **premature wear** on gears, seals, and bearings.

7. **Aftermarket Quality Variability** Some sellers (especially online marketplaces) may offer **counterfeit or low-quality replicas** posing as genuine Mercury parts. **Buying from authorized dealers or reputable marine suppliers** is strongly recommended.

8. **May Not Be Necessary for All Applications** If the engine is **already running well with stock gears**, upgrading may not provide **noticeable benefits** and could be seen as an **unnecessary expense**.

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### **Conclusion & Recommendation**

#### **Who Should Buy This Gear Set?**

**Fishing enthusiasts** looking for **better acceleration and low-end power** (e.g., for trolling, chasing fish, or quick stops).

**Boat owners converting PWCs or small outboards** where **quick response is critical**.

**Those upgrading from stock gears** (e.g., 2.5:1) to **improve maneuverability** without a full engine swap.

**DIY mechanics comfortable with basic outboard maintenance** who want a **cost-effective performance boost**.

#### **Who Should Avoid This Gear Set?**

**Boaters prioritizing high-speed cruising** (may sacrifice top-end speed).

**Those with non-T4 Mercury engines** (risk of compatibility issues).

**People who don t have experience installing outboard gears** (risk of improper setup).

**Those on a tight budget** who can t afford potential **premature wear or replacement costs**.

- **If you have a compatible T4 Mercury outboard (e.g., 40-50 HP) and need better low-end performance**, this gear set is a **solid, budget-friendly upgrade** **just ensure proper installation and maintenance**.

- **If unsure about compatibility**, **consult a Mercury dealer or mechanic** before purchasing to avoid costly mistakes.

- **For maximum longevity**, **flush the gearcase thoroughly after installation** and **use high-quality marine gear oil** (e.g., Mercury Marine or equivalent).

- **Consider professional installation** if you lack experience to **prevent alignment or torque errors**.

- **Authorized Mercury dealers** (ensures genuine parts)

- **Reputable marine supply stores** (e.g., West Marine, BoatUS, local marine shops)

- **Trusted online retailers** (e.g., Amazon, eBay with seller ratings, or specialty marine forums)

- If **top speed is more important**, a **stock or higher-ratio gear set (e.g., 2.5:1)** may be better.

- For **extreme performance**, a **full gearcase upgrade (e.g., Mercury T5/T6)** might be worth the investment.

**Bottom Line:** This gear set is a **good mid-range upgrade for T4 Mercury outboards** seeking **better acceleration without a full engine change**, but **proper installation and application are key to success**.

Details:

Just because the part looks right does not mean that Otis. They will however be in similar functioning condition. Recombine shipping on multiple items. Keeping mind that if the listing is for a used part, it used part, so there may be some minor cosmetic damage scratches/scuffs.

part #: 4344104t prices

• $250.00-$399.99

specifications ouboaen:

• for makes: Mercury
• mpn: 43-44104t
• part type: Gear

seller ouboaen:

• rating: 99.9%
• city: Melrose, Minnesota
• # reviews: 4646

shipping ouboaen:

• transit: 3-7 Days
• type: Fixed
• cost: $0.00
• class: Standard
• service: Standard

general ouboaen:

• Boat Parts > Outboard Engines Components > Other
• condition: Used

returns ouboaen:

• paid by: Seller
• policy: Returns Accepted
• time: 30 Days

offer ouboaen:

• quantity: 1
• options: Ship-to-home
• sold: 0
• started: February 2, 2026
• availability: In Stock

payments ouboaen:

• other
• wallet: Paypal
• credit card: Mastercard

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