For Supra boat owners seeking to maximize their vessel’s potential, understanding and optimizing “Supra Specs” is crucial. Performance enhancements often involve fine-tuning various aspects of the boat, and one significant area for improvement lies in propeller selection. This article explores a practical example of how a propeller upgrade dramatically altered a Supra boat’s performance characteristics.
Initially, a 1987 Supra Pirata, equipped with a Mercruiser MIE 454 engine rated at 340 hp and a 1:1 transmission, was fitted with a 14×12 3-blade propeller. This setup, intended as a baseline, revealed significant inefficiencies. The 3-blade prop resulted in excessive prop slip, ranging from 25% to 28%. This high slip rate manifested in poor handling, making the boat’s stern feel loose, especially at slalom speeds, severely hindering course navigation. At 3,750 rpm, the boat only achieved 32 mph, further highlighting the propeller’s inadequacy.
To address these performance shortcomings and refine the supra specs, a switch was made to a 4-blade Solas 13×13 right-hand rotation propeller. The impact of this change was immediately noticeable. Prop slip decreased substantially to the 13% to 15% range. The reduced aeration in the prop wash dramatically improved boat tracking and turning responsiveness. Slalom course runs became significantly easier, and overall driveability experienced a marked improvement. The owner’s sentiment shifted from considering selling the boat to enthusiastic satisfaction.
Performance metrics with the 4-blade propeller showcased notable gains:
- 2600 rpm: 28 mph
- 3000 rpm: 32 mph
- 3500 rpm: 36.5 mph
Even with added ballast for wakeboarding, the boat demonstrated effortless pull-up power, requiring minimal throttle input. Slalom ski starts were also enhanced, characterized by minimal engine rpm flare and smooth acceleration to speed. Simply bringing the rpm to approximately 3,000 to 3,100 rpm provided immediate and consistent pull.
While acknowledging a potential minor increase in fuel consumption due to the 4-blade propeller’s increased drag, the owner deemed the trade-off worthwhile, prioritizing the substantial improvements in handling and overall driving experience. High-speed wide-open throttle testing was intentionally omitted due to windy conditions, prioritizing boat safety.
In conclusion, this experience underscores the significant impact of propeller selection on Supra boat performance and “supra specs”. Upgrading to a 4-blade propeller effectively addressed issues related to prop slip and handling, resulting in a more enjoyable and capable watersports vessel.
