Under the Hood
The Belize 54 I tested was fitted standard with twin Volvo Penta IPS 800 diesel engines and pod drives (each max rated at 600 horsepower). When I arrived at the dock, Riviera/ Belize International Sales Director, Chris McCafferty, had the yacht warming up with the quarterdeck engine room hatch open. (Note that, being at one time a rag-bagger, I outright refuse to call a flush aft deck a “cockpit.”)
Big diesel iron is pretty noisy, even at idle. And generally, the bigger it is, the noisier it is. So as I dropped down the ladder into the Belize’s compact but workable engine room, I wondered whether I should have brought my ear plugs. But as my head descended below the hatch coaming, I immediately noticed how quiet the diesels were. And any lingering doubt about my need for ear plugs was dispelled entirely when I later ran the yacht at wide open throttle. But more on that later, when we talk about performance.
In the meantime, just to ensure we’re all on the same page, let me remind you that the Volvo Penta IPS incorporates an underthe-hull drive leg that carries two forward-facing, counter-rotating propellers that rotate through a full 360 degrees as directed by a fully electronic control box. The drive leg is not “hard” or “close-coupled” to the propulsion engine, but instead is attached via a jack shaft that has a universal joint at each end. This setup allows the engine to be “soft” (resiliently) mounted, which minimizes transmission of noise and vibration to the hull structure. Soft-mounting the engine is possible because, with IPS, propeller thrust is transmitted to the hull through the drive-leg mounting flange, not through the engine mounts as would be the case with a traditional setup (propshaft to close-coupled marine transmission).
The Volvo Penta IPS drive leg (called a “pod drive”) also incorporates a forward-facing propeller arrangement. This puts its props in clean, undisturbed water, in contrast to what happens when they are placed in a trailing position relative to the drive leg. The result is a significant increase in propeller efficiency. And that’s not all. The efficiency of the drive is further enhanced by Volvo Penta’s signature twin counter-rotating propeller arrangement.
I need to point out that the improved efficiency of twin counter-rotating propellers is not just empty marketing hype. When I first started testing Volvo Penta DuoProp drives for a number of boating magazines in the 1990s, I was often able to arrange to test a non-DuoProp version of the same boat at the same time. And I can say without hesitation that the differences in terms of propeller bite in fast, hard turns and during acceleration to top speed from a dead stop were significant. During my recent test of the Belize 54 Daybridge, I observed that Volvo Penta IPS takes these improvements to the next level.