MERCURY 393-3738 Outboard Bp Rotor Distributor Shaft Spacer 1350 1250

( Manufacturer Part Number: 393-3738 ), ( Part Type: Rotor Distributor Shaft Spacer )

Review MERCURY Outboard 1350 And Others Bp Rotor Distributor Shaft Spacer Nice

The **Mercury 393-3738 Outboard Distributor Shaft Spacer** is a precision-engineered component specifically designed to maintain optimal mechanical alignment and performance within the **1350 and 1250 series two-stroke outboard motors** produced by Mercury Marine. This critical spacer serves as an integral part of the rotor distributor assembly, ensuring proper spacing between the distributor shaft and the rotor housing to prevent binding, excessive wear, or misalignment all of which could lead to reduced engine efficiency, erratic ignition timing, or even catastrophic failure. Crafted from high-grade, durable materials, this spacer is engineered to withstand the demanding conditions of marine environments, including exposure to saltwater corrosion, vibration, and thermal fluctuations. Its precise dimensions are meticulously calibrated to match Mercury s original equipment specifications, guaranteeing a seamless fit within the distributor assembly while allowing for smooth rotational movement of the rotor. By maintaining the correct axial clearance, this spacer helps preserve the integrity of the ignition system, ensuring consistent spark delivery to the combustion chamber for reliable power output. Whether used in recreational boats, fishing vessels, or performance watercraft, this part is essential for preserving the longevity and performance of the outboard s ignition components, ultimately contributing to smoother operation, reduced maintenance requirements, and enhanced reliability over time. For marine enthusiasts and professionals seeking to restore or upgrade their Mercury outboards, this distributor shaft spacer is a straightforward yet vital replacement that upholds the engine s factory-intended specifications.

The **Mercury 393-3738 Outboard Motor** (specifically the **1350 RPM rotor distributor shaft spacer**) is a critical component for maintaining proper timing and performance in older Mercury outboards, particularly those from the mid-2000s era. Below is a detailed breakdown of its pros and cons, followed by a conclusion and recommendation.

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### **Pros of buying a Mercury 393-3738 Shaft Spacer**

1. **Restores Proper Timing**

The shaft spacer ensures the distributor rotor aligns correctly with the ignition system, preventing misfires, rough idling, or failure to start. Worn or missing spacers can lead to catastrophic engine damage if left unaddressed.

2. **Prevents Engine Damage**

Incorrect timing due to a missing or improper spacer can cause severe internal wear, including damage to pistons, valves, or the crankshaft. Replacing the spacer is a cost-effective preventive measure compared to major engine repairs.

3. **Compatibility with Aftermarket Ignition Systems**

If you re upgrading to an aftermarket ignition kit (e.g., for better performance or reliability), the correct spacer is essential for proper installation and function.

4. **Easy to Install**

The spacer is a simple bolt-on part that requires minimal tools (a socket wrench and possibly a torque wrench). Installation typically takes less than an hour, even for less experienced DIYers.

5. **Affordable Replacement Cost**

Compared to the potential cost of engine failure, the spacer is relatively inexpensive usually ranging from $20 to $50, depending on the source (OEM vs. aftermarket).

6. **Extends Engine Life**

By maintaining precise ignition timing, the spacer helps keep the engine running smoothly, reducing wear on other components like spark plugs, coils, and fuel injectors.

7. **Common Part with Wide Availability**

Mercury outboards from the 2000s 2010s share many components, so finding a replacement is straightforward through dealers, online marketplaces, or specialty marine parts stores.

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### **Cons of buying a Mercury 393-3738 Shaft Spacer**

1. **Potential Counterfeit or Low-Quality Parts**

Some aftermarket or eBay listings may sell knockoffs that don t meet OEM specifications. A poorly made spacer could cause timing issues or fail prematurely, leading to further problems.

2. **Requires Basic Mechanical Knowledge**

While the installation is straightforward, removing the old spacer may require disassembling parts of the ignition system or lower unit. Those unfamiliar with outboard maintenance might struggle without guidance.

3. **Not a Permanent Fix for Underlying Issues**

If the distributor itself is worn or the ignition system is failing, replacing just the spacer won t solve deeper problems. A full ignition overhaul may eventually be needed.

4. **Limited Lifespan**

While the spacer itself is durable, other components (like the distributor rotor or pickups) may degrade over time. The spacer may need replacement again if these parts fail.

5. **Risk of Over-Tightening**

Improper torque on the spacer bolt can strip threads or damage the distributor housing. Using the correct torque specification (if available) is crucial.

6. **May Not Improve Performance Significantly**

If the engine was running fine before the spacer was lost or worn, replacing it won t provide noticeable performance gains only reliability and preventative benefits.

7. **Depends on Other System Components**

If the spark plugs, coils, or fuel system are neglected, replacing the spacer alone won t optimize engine performance. A holistic approach to maintenance is ideal.

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### **Conclusion**

The **Mercury 393-3738 shaft spacer** is a **highly recommended** part to purchase if you re experiencing ignition-related symptoms (misfires, rough idle, no-start conditions) or if you re upgrading your ignition system. It s a **low-risk, high-reward** replacement that prevents costly engine damage and ensures proper timing. The installation is simple, and the part is widely available, making it a practical choice for DIYers and professionals alike.

However, if you re unsure about the condition of your distributor or other ignition components, it may be worth inspecting those as well to avoid recurring issues. Always source the part from a reputable supplier to avoid counterfeit or substandard components.

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### **Recommendation**

1. **Purchase from a Trusted Source**

Buy the spacer from an **authorized Mercury dealer**, a **specialty marine parts store**, or a well-reviewed online retailer (e.g., **Mercury Marine s official site, West Marine, or eBay with verified sellers**). Avoid suspiciously cheap listings that may be counterfeit.

2. **Verify Part Compatibility**

Double-check that the **393-3738 spacer** is the correct part for your specific outboard model (e.g., 4.6L, 5.0L, or other variants). Some engines may require slightly different spacers or additional components.

3. **Follow Installation Guidelines**

Refer to your **outboard s service manual** or a **reliable online guide** (e.g., Mercury s technical bulletins) for step-by-step instructions. Pay special attention to torque specifications if applicable.

4. **Inspect Related Components**

- **Distributor rotor and cap** for wear or cracks.

- **Ignition pickups** for damage or signal loss.

- **Spark plugs** for fouling or improper gap.

- **Fuel system** for clogs or pressure issues.

5. **Test After Installation**

- Smooth idle and acceleration.

- No misfires or hesitation.

- Proper RPM response.

6. **Consider a Full Ignition Upgrade (If Needed)**

If your outboard is older and the ignition system is failing, investing in a **high-quality aftermarket ignition kit** (e.g., **Mercury s own upgraded systems or brands like SeaStar**) may be more cost-effective long-term.

**Final Verdict:** **Buy the spacer if you re experiencing timing-related issues or upgrading your ignition system.** It s a **necessary preventive measure** that costs pennies compared to the potential cost of engine failure. Just ensure you source it properly and address any accompanying wear in the ignition system.

Details:

Make sure this is correct for your application. Where used says it fits the 1150 and 1250 BP also. Does have 1 very minor chip by the brass tip see pics. Part number is 393-3738.

This is the earlier version with a single brass point not dual prongs like later model's. The shaft is in good shape, shows signs of use, threads and nut are there no cracks the rotor. Included are the nut and long spacer.

part #: 3933738 prices

• $21.93-$149.97

specifications ouboaen:

• for makes: Mercury
• mpn: 393-3738
• part type: Rotor Distributor Shaft Spacer

offer ouboaen:

• started: April 10, 2026
• sold: 0
• quantity: 1
• best offers: True
• availability: In Stock
• options: Ship-to-home

shipping ouboaen:

• service: USPS Priority Mail Small Flat Rate Box
• transit: 5-8 Days
• carrier: USPS
• class: Expedited
• cost: $9.95
• type: Fixed

returns ouboaen:

• policy: Returns Accepted
• paid by: Buyer
• time: 14 Days

payments ouboaen:

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

general ouboaen:

• Boat Parts > Outboard Engines Components > Ignition Starting Systems
• condition: Used

seller ouboaen:

• # reviews: 2417
• city: Saint Cloud, Minnesota
• rating: 100.0%

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