Author: Jeff Magusin
Repowering marine vessels with modern low-emission engines not only helps save the environment, but often makes good economic sense. However, making sure the transmission is efficiently integrated into the propulsion package is the key to success.
Before doing a repower, you should meet with your marine transmission supplier early in the design stage to ensure the gear system is efficiently integrated into the propulsion package. Also, be sure to check the Carl Moyer Program for the requirements for marine and vessel projects before you begin.
How to Ensure Your Repowering Is a Win-Win
Engine Rating Changes: New engines being used in repowers may incorporate a change in horsepower rating and peak RPM. Both of these are considerations that could change the model and ratio of the marine transmission required for the application.
The Propeller: Propeller shape and design for the vessel should also be considered - as it is a key element to proper performance. The original propeller design is based upon the propulsion packages’ original engine rating and transmission gear ratio. Any change to this combination could lead to unsatisfactory vessel performance.
Torque Requirements: New engines have higher horsepower available to them at different RPM’s, changing the torque requirements on the marine transmission. This means that an older transmission may not be suitable to work with a newer engine. Failure to address this could lead to early failure and significant damage or downtime.
Footprint and Fit: The current engine footprint is likely different than the replacement. Changes to the engine centerline should be addressed early on in the process, as the offset to the prop shaft is set by the marine transmission. Raising or lowering the engine could require modifications to the vessel, however it is possible that a different offset in the marine transmission could help to resolve this issue.
Torsional Vibration: In general, new engines are more torsionally active than older engines. The new transmission models include torsional couplings that dampen the high torsional activity of the Tier 2, Tier 3 and Tier 4 engines. Without the proper torsional coupling vibration analysis, transmission life can be compromised. Torsional vibration failures are not covered under warranty and usually fail within the first 4,000-5,000 hours in service.
Obsolete Gears: Many older transmissions are obsolete, and have been replaced with newer models, therefore parts availability can be an issue. In addition, older transmissions coupled with newer engines could increase power demand issues, resulting in downtime. New transmissions come with a torsional coupling and a factory warranty to match your engine, ensuring long-term durability.
New Technology: Newer Twin Disc transmissions are available with electric proportioning valves that allow for more efficient shifting and electronic propulsion control systems which can eliminate the possibility of operator error and clutch pack failure. They also provide a safer and more efficient operation at low speed. This option allows for better performance and maneuverability at low speeds, especially in trolling mode.
There is a very valid environmental and economic case to be made for repowering marine vessels. Paying close attention to transmission considerations ensures your repowering will not only be a successful, but save you money. A win-win!