Lone V8 the star of this cruiser

Southstar 37. Photo / Supplied

The Southstar 37 is an 11m sedan-style cruiser produced by Greg Salthouse at Salthouse Boatbuilders in Greenhithe, on Auckland's North Shore.

It is, by the standards of production boatbuilding in New Zealand, a reasonably successful model. The company has just launched its fourth 37, and four boats of one model is still a lot better than the average these days.

While the previous three versions were all powered by a 450hp Yanmar diesel engine (through conventional shaft drives), this latest version has a single V8 Yamaha 350hp outboard.

Powering an 11m launch with an outboard or two is not new. The larger-than-life Ken Lusty famously installed two Yamaha outboards on the back of one of his Horizon launches and then followed that with a slightly bigger version, with three Yammies hanging off the transom.

The difference here is that, to the naked eye, this Southstar looks remarkably similar to its predecessors. There is no outboard protruding from the stern, its transom is flush and there is a full-length boarding platform.

Salthouse has instead installed the big V8 in its own box at the back of the cockpit. While this does use up some space, it makes up for that by providing a finished flat surface suitable for use as a bait board or a table when dining.

In addition, the space required for the V8 Yamaha is nothing like that needed for a big 450hp inboard. For "a small sacrifice of space", Salthouse said he was able to fit an extra double bed in the guest cabin and gained extra storage space.

However, money was the main motivation for switching from inboard to outboard. Salthouse estimates he saved about $150,000 on the engine package and also saved about 550 hours in the construction of the boat and the installation of the engine and drive-train package.

Where he would have had to install the engine, gearbox, shafts, couplings and propellers, he instead had only to connect the outboard. It was fitted in a single morning.

Another advantage is in upkeep. "The fact that we can tilt the motor completely out of the water when at rest means we have no running gear sitting underwater," says Salthouse. "Service is that much easier and quicker than with an inboard diesel."

There is also the question of weight. An inboard Southstar 37 has a displacement of about 7000kg - the outboard powered one is closer to 6000kg. Of course, it is not entirely a one-way street. Petrol costs considerably more per litre than diesel, and with an outboard you need more fuel to travel the same distance.

However, even when Lusty was doing his thing with outboards on launches, he reasoned that the initial savings on the installation of outboards far outweighed their running costs.

That still holds true today, and $150,000 (plus those 550 hours) will certainly buy a lot of petrol, even at today's inflated prices. The equation looks even better now as these new-generation, four-stroke outboards are far less thirsty than Lusty's old two-strokes.

On his shakedown cruise over Christmas, Salthouse found that the outboard-powered Southstar used 850 litres for 50 hours of running, at an average of 17 litres per hour.

"Most of our cruise passages were around 3800-4000rpm," he says. "This gave us around 18 knots, although when we were gunkholing in the Bay of Islands and Great Barrier, a lot of the time we were under 10 knots."

One advantage that Salthouse probably hadn't anticipated is that the Southstar is so fun to drive. The 5.3-litre V8 Yamaha 350 has enough torque throughout the range to ensure that this 11m cruiser performs with the agility of a 6m runabout.

Salthouse has also added a Permatrim wide-body trim tab to the engine. He says this has eliminated any prop ventilation in tight cornering and has improved the low-speed tracking.

Pacific Motoryacht editor Barry Thompson has reviewed both the inboard and outboard versions of the Southstar 37. He says the only noticeable difference in the handling is that the outboard proves more nimble at low speeds. At high speeds, he says, both handle much the same although the outboard is noticeably more responsive.

Of course, the low noise output of these big, modern four-stoke outboards is near legendary and this V8 is no exception. At 2000rpm, there is just 71dBA at the helm (rising to 78dBA at 2500rpm). At 4000rpm, doing 18 knots and with the rear doors and windows removed, the decibels increased to just 86dBA.

With the 350hp V8, the Southstar can hit a top speed of 24.5 knots. For those of a more sedate nature, a single 300hp outboard or even a 250hp model would still give a top speed in the low 20s, and there is also enough space to fit a pair of 150hp or 175hp outboards.

The Southstar 37 is, of course, still available as a traditionally shaft-driven inboard diesel boat. Those with a more adventurous bent can also opt for a V-drive, twin or single sterndrives or even pod drives.

Regardless of the motor choice, the design is finding favour both here and overseas.

Southstar 37
(V8 outboard powered)

LOA: 11.15m

Beam: 3.91m

Draft: 600mm (engine down)

Displacement: 6000kg

Construction: Epoxy composite

Engine: Yamaha 350hp V8

Max Speed: 24.5 knots

Cruise Speed: 18 knots

Fuel Cap: 1200 litres

Water Cap: 600 litres

Want to know more?
Check out the review of the new outboard-powered Southstar 37 in the March/April issue of Pacific Motoryacht magazine.