MERCURY B742 Clymer Stern Drive Manual Alpha Bravo 024185755340

( Manufacturer Part Number: B742 ), ( Part Type: Drive Manual ), ( Country Of Origin: United States ), ( UPC: 024185755340 )

Review MERCURY Clymer Stern Drive Shop Manual Alpha One And Bravo fits MERCRUISER 1986–1990

The **Mercury B742 Clymer Mercruiser Stern Drive Manual (1986 1990 Alpha Bravo)** is an indispensable, meticulously crafted resource designed for mechanics, DIY enthusiasts, and boat owners seeking comprehensive guidance on servicing, repairing, and maintaining their Mercury Alpha Bravo stern drive models from the late 1980s. This edition is a direct adaptation of the legendary *Clymer* series, renowned for its unparalleled depth and clarity, ensuring that even those with limited mechanical experience can confidently tackle tasks ranging from routine maintenance to complex overhauls. The manual covers every critical component of the B742 engine and stern drive system, including the powerhead, transmission, lower unit, steering linkage, trim and tilt mechanisms, and associated electrical systems, all of which are meticulously detailed with step-by-step instructions, precise torque specifications, and annotated diagrams that break down disassembly, inspection, and reassembly processes. Whether you're troubleshooting a persistent issue like a rough idle, diagnosing a transmission shift problem, or performing a full engine flush and oil change, this manual provides the exact procedures required to restore peak performance and reliability. The coverage extends beyond mechanical components to include essential topics such as fuel system maintenance, cooling system diagnostics, and propeller alignment, ensuring that every aspect of the stern drive s operation is addressed with professional-grade precision. Ideal for both professional technicians and dedicated hobbyists, this manual bridges the gap between generic repair guides and manufacturer-specific documentation, offering a trusted, independent resource that stands the test of time. With its durable, spiral-bound format and durable paper stock, it is built to withstand repeated use in workshops, garages, or on the dock, making it an essential addition to any boater s toolkit.

### **Pros and Cons of Buying a Mercury B742 (Clymer Mercruiser Stern Drive Manual, 1986 1990 Alpha Bravo)**

#### **Pros**

1. **Reliability and Durability** The B742 is a well-regarded inboard/outboard engine known for its robust construction and longevity, especially when properly maintained. Many units from this era have lasted decades with minimal major issues if cared for.

2. **Power and Performance** With **225 250 horsepower**, this engine provides strong acceleration and cruising power, making it suitable for mid-sized boats (20 28 feet) like bass boats, fishing vessels, or small cruisers. It handles well in both planing and cruising modes.

3. **Proven Design** The **Alpha Bravo** series (1986 1990) was an evolution of Mercury s earlier designs, incorporating improvements in fuel efficiency, cooling, and drivetrain reliability. The **B742** was a popular choice for its balance of power and fuel economy compared to larger engines.

4. **Aftermarket Support** Being a classic Mercury, parts are still available through specialty marine suppliers, eBay, and salvage yards. The **Clymer manual** you referenced is a valuable resource for DIY maintenance, repairs, and troubleshooting.

5. **Lower Operating Costs (Compared to Modern Engines)** Fuel efficiency was better in the late '80s than in some modern outboards, and maintenance costs (when done preventatively) are often lower than high-performance or diesel alternatives.

6. **Classic Boat Appeal** If you re restoring or running a vintage boat, this engine fits well with the era s aesthetic and mechanical simplicity. It s a great choice for enthusiasts who appreciate mechanical challenges and the satisfaction of working on a well-built machine.

7. **Stern Drive Advantages** The **Mercruiser stern drive** (I/O) offers better maneuverability than a straight shaft, making it ideal for fishing, docking, and tight spaces. The **B742** was designed for this application, ensuring smooth power delivery.

8. **Potential for Modifications** With a manual like the Clymer, you can upgrade components (e.g., exhaust, fuel system, or drive unit) to improve performance or reliability. Tuning options (like carburetor adjustments) are straightforward compared to modern fuel-injected engines.

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#### **Cons**

1. **Age-Related Wear and Tear** Engines from this era have likely accumulated **20,000 50,000 miles** (or hours), meaning components like **pistons, bearings, seals, and the drive unit** may need replacement. A thorough inspection is critical before purchase.

2. **Fuel System Issues** Carbureted engines (common in this era) are prone to **fuel line leaks, clogged jets, or carburetor failure**. Modern fuel systems (like EFI) are more reliable but require different maintenance.

3. **Cooling System Concerns** Older Mercurys often suffer from **rusted raw water pumps, impeller wear, or overheating** due to degraded seals or clogged heat exchangers. The **drive unit s cooling fins** can also corrode over time.

4. **Electrical Problems** Wiring harnesses, starters, and alternators may be worn out. Corrosion in electrical connections is a common issue in marine engines, especially if the boat has been stored improperly.

5. **Drive Unit and Lower Unit Wear** The **stern drive s drive unit (gearbox) and lower unit (propeller housing)** can fail if not maintained. Signs of trouble include **grinding noises, oil leaks, or difficulty shifting**. Rebuilding or replacing these can be expensive.

6. **Emissions and Modern Regulations** While not an issue for recreational use, some older engines may not meet current **EPA or state emissions standards** if modified or used in certain areas. Check local laws if you plan to use it in regulated waters.

7. **Fuel and Oil Compatibility** Older engines often require **specific grades of oil and fuel** (e.g., 2-cycle oil for outboard components if still used). Modern fuels (with ethanol) can degrade rubber seals and varnish carburetors.

8. **Parts Availability and Cost** While parts exist, some **specialty items (e.g., OEM gaskets, seals, or drive unit components)** may be hard to find or expensive. Salvaging parts from a similar engine can be cost-effective but time-consuming.

9. **Learning Curve for Maintenance** Without mechanical experience, diagnosing and fixing issues (e.g., vacuum leaks, drive unit failures) can be challenging. The **Clymer manual** helps, but some problems may require a marine mechanic.

10. **Potential for Hidden Damage** Rust, cracked casings, or internal corrosion (especially in the **cooling system or drive unit**) may not be visible during a quick inspection. A **pressure test, oil analysis, and drive unit inspection** are essential before buying.

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### **Conclusion**

The **Mercury B742 (1986 1990 Alpha Bravo)** is a **solid, powerful engine** that remains a great choice for **fishing boats, cruisers, or restoration projects** provided it is **thoroughly inspected and maintained**. Its **reliability, power, and aftermarket support** make it a strong contender for those who appreciate classic marine engines. However, **age-related wear, potential electrical/fuel issues, and the need for preventive maintenance** mean it requires **more attention than a new engine**.

If you re **mechanically inclined, willing to invest time in upkeep, and can afford potential repairs**, this engine is an excellent **budget-friendly powerplant** with a lot of character. For **casual boaters or those seeking low-maintenance operation**, a **modern outboard or a well-maintained used engine from the 2000s onward** might be a safer bet.

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### **Recommendation**

- **Drive unit condition** (listen for grinding, check for leaks).

- **Cooling system** (raw water pump, impeller, heat exchanger).

- **Electrical system** (test starter, alternator, wiring).

- **Fuel system** (carburetor condition, fuel lines, hoses).

- **Oil analysis** (check for metal particles indicating wear).

- **Budget for repairs** expect to spend **$1,500 $4,000 ** on a rebuild or major overhaul if the engine is neglected.

- **Test the engine in water** (if possible) to ensure smooth operation and no unusual noises.

- This engine is an **excellent fit** for a **classic boat** if you enjoy mechanical work and want a **unique, powerful setup**. Pair it with a **Clymer manual** and a **marine mechanic s help** for critical repairs.

- Consider a **modern outboard (e.g., Yamaha, Mercury, Suzuki from 2010 ) or a well-documented used engine from the 2000s** with **full service records**. These will require less work but offer similar power.

- **Fishing enthusiasts** who want a **reliable, high-torque engine** for bass boats or live wells.

- **Boat restorers** who appreciate **mechanical challenges and classic marine engineering**.

- **Budget-conscious buyers** who are **prepared for maintenance** and can handle occasional repairs.

- You **don t have time or mechanical skill** for regular upkeep.

- The engine has **visible rust, leaks, or a history of neglect** without proof of recent maintenance.

- You **prioritize convenience** over character modern engines offer **fewer repair headaches**.

**Final Verdict:** The **Mercury B742 is a fantastic engine for the right owner** one who values **performance, reliability, and the satisfaction of working on a well-built classic**. With **proper care, it can easily last another 20 years**, making it a **wise investment for the mechanically inclined**. However, **expect to spend time and money on maintenance** to keep it running smoothly.

Details:

I work hard to include several pictures of each item. See pictures. I do my best to describe the items and their conditions. Good used condition.

Great care is taken when packaging every item to ensure safe quality shipping. Unless stated.

part #: b742 prices

• $10.00-$24.95

specifications ouboaen:

• for models: Mercruiser
• for makes: Mercury
• for years: 1986-1990
• mpn: B742
• part type: Drive Manual
• country of origin: United States
• upc: 024185755340

general ouboaen:

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

returns ouboaen:

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

seller ouboaen:

• city: Charlevoix, Michigan
• rating: 100.0%
• # reviews: 2000

payments ouboaen:

• wallet: Apple-pay
• credit card: Diners-club
• other

offer ouboaen:

• availability: In Stock
• quantity: 1
• sold: 0
• started: May 11, 2026
• options: Ship-to-home

shipping ouboaen:

• carrier: USPS
• class: Economy
• cost: $6.72
• transit: 3-8 Days
• service: USPS Media Mail
• type: Calculated

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