Ship quieting technology

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Information about technologies that have been proven to reduce underwater noise in ships and boats. The emphasis here should be on practical solutions that make economic sense to boat owners.

Thanks to Brandon Southall of NOAA for coordinating the conferences on this subject and for distilling much of these data and resources! As I wrote to him, "It would be *great* if there were some case studies that include cost/benefit analysis of particular quieting technologies (including practical manufacturer-model-number-type specifics)." Let's try to focus on such information here. Special thanks to Todd Shuster of Gato Verde Sailing Adventures for providing a list of his favorite potential quieting technologies.


  • Endangered southern resident killer whales use sound for communication and foraging
  • Ships and boats dominate the noise budget within killer whale critical habitat
  • It is relatively feasible to mitigate the risk of acoustic impacts (compared with risks due to salmon depletion and persistent pollutants)
    • Recreational retrofits are possible
    • Commercial whale watching vessels could be quieted
    • WA State ferries are being replaced
    • Commercial ships transit critical habitat ~20 times/day

International workshops and agreements

Ships (large vessels)

Boats (small vessels)

 Existing prototypes fit:
 Mercury Bravo II
 Konrad stern drive (240-260 series)
 Evinrude 150 hp to 250 hp

Evinrudes generally run relatively smaller propellers in the 150-250 hp class, which is compatible with the Thrustor and the necessary propeller clearances. Bravo II and Konrad usually are heavier vessels with bigger hp and a need for maximum prop surface for max performance. The Thrustor for these boats is 19.5" inside diameter (I.D.). One inch to 1.5" clearance is necessary to prevent pressurizing the nozzle system and adding unnecessary prop torque. It is recommended to use 16.5-17.5" diameter props.

  • Durajet propless pump jet propulsion system (Florida)| re-seller (no noise reduction results as of 10/2008).
 Compatible engines:
 Evinrude E-Tec Tiller 40, Remote 40, 50, and 60HP
 Johnson Commercial Tiller 20, 30, 35, 55, Remote 60 and 70HP
 Mercury Tiller and Remote 2-stroke and 4-stroke 40
 Tohatsu/Nissan 2 and 4-stroke 25 and 30HP remote and tiller

Notes on other technologies to consider

  • Power pods (attach to trim tabs or anti-cavitation plates
 Minn Kota -- trimtroll | Riptide (transom-mounted) | RipTide ST (bow-mounted)
 Marine Tech navigator
 Motor Guide 
  • Electric outboards:
 Solid Nav
  • Kort nozzles (often used on tugs and research vessels)
  • Vetus in-line hybrid (~4hp? Probably too small for most whale watch vessels, but good for small sailboats; Fisheries Supply may carry)
  • Berkeley jet?
  • Bigger systems for inboard or I/O repower or new builds, 20-50' displacement hulls:
 Solid Nav
 e-Power E-pods
 Whisper Prop (Germany)
  • Even bigger systems
 Ossa Powerlite
 Siemens for big boats 125hp and up

Thought from Todd: "Theoretically a 330VDC AC propulsion system that could be very powerful, efficient, waterproof and cool (brushless PM AC motor) could be done with off the shelf components for under $10K...I'm just not willing to carry that voltage aboard at this time and finding a generator to charge and regulate that pack would be a very custom creation. It would probably be easiest to power a system like this with a standard 220AC generator and a smart charging system that could boost the voltage."