Unsure if this would scale up but as others have mentioned for large ships the operation is very sensitive to cost. Fuel efficiency is weighed against current fuel cost, cost to design a technology into a new ship or retrofit, maintenance, etc. That said, since fuel rates are high and emissions regulation is set to come into effect soon [1] you'll likely see waves of shipbuilders adopt fuel-saving technology.
A few problems that might show up with this type of prop/"screw" on a large ship:
- Ship propulsion uses a fairly large-diameter prop and runs at very low RPM (~100rpm vs 1000-6000rpm) compared to smaller planing vessels. The Sharrow prop advertises decreased cavitation at high speeds but this effect may be diminished at low RPM.
That said, cavitation is a different beast for ships than for recreational boats: In the recreational market few boat owners are concerned about propeller efficiency loss due to cavitation -- Concern is mostly around noise and vibration. In contrast, ships are very concerned with fuel and maintenance cost, so if the Sharrow blade successfully reduces both of these it may be helpful.
- Seems like they're currently machining these on a 5-axis CNC out of blocks of raw material which won't scale to larger sizes. The complicated shape may not lend itself as well to casting, and even if they casted the shape it would need to be finished and this would require expensive equipment.
- Might be more difficult for third-party repair [2] which is done manually or with 3-axis machines.
Generally the commercial maritime market is much slower to adopt new technology than recreational, and also much smaller by volume, so it may make sense for Sharrow to continue serving small outboard boats because margins + sale volume is much higher.
