We conducted a theoretical analysis to examine the performance of Mercury Racing APX Outboards (200 V6, 250 V8, and 360 V8 models) and the seven (7) available OEM gear ratios from the Factory. These gears can be changed in the overdrive box!
We factored in the 1.13 final drive ratio found in the current SuperSpeed Master #4 (SSM4) drive, an 18-pitch propeller, and a typical 20% propeller slip found on F1 Tunnel Boats. The impact of these configurations on speed and torque provides insights for optimizing race setups.
Mercury Racing APX Gear Ratios and Performance Data
The table below presents the adjusted gear ratios, peak propeller shaft speeds, and calculated top speeds for V8 and V6 engines:
Gear Ratio | Overall Ratio (1.13) | Peak Prop Shaft Speed (V8) | Peak Prop Shaft Speed (V6) | Top Speed (V8, mph) | Top Speed (V6, mph) |
0.667 | 0.754 | 9,259 | 9,055 | 126.26 | 123.48 |
0.714 | 0.807 | 8,756 | 8,564 | 119.40 | 116.78 |
0.724 | 0.818 | 8,672 | 8,483 | 118.25 | 115.68 |
0.739 | 0.835 | 8,483 | 8,302 | 115.68 | 113.21 |
0.765 | 0.864 | 8,191 | 8,024 | 111.70 | 109.42 |
0.786 | 0.889 | 7,987 | 7,823 | 109.05 | 107.00 |
0.818 | 0.926 | 7,718 | 7,551 | 105.85 | 103.55 |
Key Findings
Maximizing Top Speed:
The 0.667 gear ratio delivers the highest top speed for both V8 and V6 engines, reaching 126.26 mph (V8) and 123.48 mph (V6). This configuration is best for flat-water or top speed racing.
Prioritizing Torque and Acceleration:
Higher gear ratios like 0.765, 0.786, and 0.818 provide more torque at the expense of top speed. These configurations excel in rough water or technical courses requiring rapid acceleration and precise handling.
Balanced Configurations:
Ratios such as 0.724 and 0.739 (Stock on the APX 360) offer a balance of speed and torque, making them suitable for circuits with mixed conditions, including straights and tight turns.
Effect of the 1.13 Final Drive Ratio:
The final drive ratio slightly reduces prop shaft speeds to better match prop speeds found on the legacy 2-stroke S3000, F1 and SST-120 while enhancing durability and efficiency, ensuring consistent performance under demanding conditions.
Practical Applications for Racers
Top Speed: For straight-line speed dominance, the 0.667 gear ratio is ideal, especially in calm water with minimal resistance.
Technical Race Courses: In courses with sharp turns or rough water, ratios like 0.786 or 0.818 (Stock on the APX 200 V6 and APX 250 V8) improve acceleration and cornering capabilities.
Class-Restricted Competitions: The APEX 200/250 engines with the 0.818 ratio provide dependable torque for restricted power classes, while the APX 360 with the 0.739 thrives in high-performance scenarios with lower gear ratios.
Conclusion
The choice of gear ratio is critical for achieving the desired balance of speed and torque. With an 18-pitch propeller and 20% slip, racers can fine-tune their Mercury Racing APX outboards to excel in specific racing conditions.
By leveraging the insights from this analysis, crew chiefs and boat racers can optimize their configurations for maximum performance and competitive advantage.
Check out our New DDT Scan Tool for the APX 200, 250, and 360!
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