Contra-rotating marine propellers

After the Volvo Penta patents ran out, Mercury Marine has also produced a corresponding product, MerCruiser Bravo 3.

However, in commercial ships and in traditional machinery arrangement, contra-rotating propellers are rare, due to cost and complexity.

ABB provided an azimuth thruster for ShinNihonkai Ferries in form of the CRP Azipod,[2] claiming efficiency gains from the propeller (about 10% increase[3]) and a simpler hull design.

Volvo Penta have launched the IPS (Inboard Performance System),[4] an integrated diesel, transmission and pulling contra-rotating propellers for motor yachts.

At lower power levels, contra-rotating mechanical azimuth thrusters are one possibility, convenient for CRP due to their inherent bevel gear construction.

A Mark 46 Mod 5A torpedo is inspected aboard a destroyer in April 2005