Pacific 62 - Shafts, Props, and Engines: Our Perspective on the Matter

A significant amount of effort has gone into perfecting this system. "Perfection" is a bold term, but we genuinely believe we've achieved it.

When discussing vessels intended for remote global locations, the engine and driveline always become focal points. I've participated in numerous such discussions and operated a variety of boats with different configurations. These experiences have informed our perspective.

To understand our choices, let's strip things back to the essentials: a reliable, simple, and efficient drivetrain.

Single or Dual Drivetrain?

There are arguments for both. However, two drivetrains are superior, especially if they operate independently.

Many vessels traverse the globe with a single engine. Yet, a good proportion of modern dedicated passage-makers have a primary engine and a backup "wing" engine.

The primary advantage of a single engine is efficiency. It only requires maintenance for one engine and drivetrain, and there's only the drag of one keel, prop, and rudder. However, the wing engine, while enhancing safety, does compromise some of these benefits.

My primary concern is the potential unreliability of a seldom-used wing engine. And if your rudder is compromised, navigating becomes a challenge.

Are We Ready for Electric?

I won't delve too deeply on this topic, but I've spent a considerable amount of time exploring the subject.

For ocean-going vessels, you often end up with a diesel-electric drivetrain. Batteries and solar can provide some power, but for extended journeys, diesel's reliability is unmatched.

Current developments focus on DC motors, and the available systems aren't sufficiently tested for our needs. While alternative fuels and electric drives will become standard in the future, we're not there yet.

Engine Size?

Given the vessel's multifunctional use, we wanted the ability to cruise at 12-14 knots occasionally, with a primary speed range of 7-9 knots.

We delved deeply into achieving two operational modes for the vessel, even running Computational Fluid Dynamics (CFD) simulations for both speeds.

We designed our water tanks at the vessel's extremities for optimal trim. The horsepower required for the higher speed would mean the engines would idle at the lower speed, which isn't ideal. The engine we chose can easily handle the lower range.

So, our ideal drivetrain?

We've opted for two engines, shafts, props, and rudders, with two independent fuel and power systems.

A significant advancement was the variable pitch propeller system, which operates from near zero drag to full forward pitch. This allows us to run on a single engine for long passages or trolling and use both engines for faster speeds. We can also adjust to speeds as low as 0.5 knots, effectively anchoring over deep-sea reefs overnight.

This system ensures efficient engine operation and doubles our service intervals. Additionally, our twin keels allow the vessel to dry out and rest stably, ideal for cleaning in a tidal lagoon.

While there are many valid arguments and options available, and some might excel in specific areas, we believe that in terms of reliability, simplicity, and efficiency, we've found our perfect drivetrain.

If you'd like to discuss some of this reasoning in more detail and how it might apply to your build, give us a call on the details below.

Jason Dickey - Cofounder, Dickey Boats