Southern XP716 Diesel

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Southern XF 676

Fresh off testing the Southern XF 676, Freddy Foote looks at a newly released variation, the XP 716 Diesel, one of the first trailerable powerboats in New Zealand with a Hyundai SeasAll D170.

The pros and cons of running a petrol outboard compared to a diesel inboard stern drive in a trailer boat has long been debated and I am not really sure there is a definitive answer.

Many manufacturers offer model in either diesel stern drive or petrol outboard configurations and while the outboards dominate, there is a move, albeit small towards the diesel option.

It’s not often we get to sample both configurations in an almost identical model and report back the results. In this case we have put the Southern XF 676 with a Yamaha 150hp four-stroke outboard up against a Southern XP 716 Diesel, powered by a Hyundai SeasAll S170. Essentially they are the same hull, albeit the diesel version is a little longer and both engines are comparable horsepower.

Layout

From mid cockpit both boats largely share the same layout configuration.

Forward in the open cabin, a large vee berth converts to a double with the addition of an infill. The cabin is fully lined with carpet giving a warm feel. Storage is available underneath the bunks, as well as on side shelves. An electric toilet is fitted under the bunk to starboard, and by sliding the cabin door shut, it provides plenty of privacy. Above, a large hatch opens to the foredeck where a Maxwell winch takes care of anchoring.

The helm seating is made up of a pedestal seat, mounted on a base with storage underneath. The seating position gives the skipper a great-unobstructed view forward through the windscreen and when standing there is plenty of headroom, so the very tallest among us will be able to stand to drive very easily.

The dash itself is neatly finished with a Raymarine 9” cSeries GPS/Sounder, whilst a switch panel and Maxwell anchor winch controls are located below.

On either side of the helm area are handy and convenient cubbyholes for storing keys, phones and the likes. On the port side, seating is made up of a pedestal seat mounted on a base with storage underneath. However, this side gets an aft facing passenger seat as well.

The cockpit has high gunwales with thigh padding to assist anglers. Carpeted cockpit shelving takes care of storage for rods; additional rod storage is located above via the rocket launcher as well as in the coamings and at the bait station aft.

The obvious prominent feature of the cockpit is the engine box, covering the Hyundai diesel. The hatch lifts forward for easy service, and above is padded for seating comfort. Overall I didn’t think the engine box was too obtrusive for the cockpit, as was still adequate room for four anglers.

A walk-through in the starboard corner gives easy access to the full width-boarding platform and accompanying dive ladder that can be shut off by inserting the gate. A wash down hose for the cockpit is also located here, allowing quick and easy cleanup of the working area. On the port side of the transom is a sizeable live bait tank with viewing window.

Pick Your Power

The standard and minimum power rating for the Southern 676 hull is 150hp., although it will happily handle up to 200hp outboards. Punch out of the hole with a 150 Yamaha four-stroke was great and helped propel the 676 to a top speed of 42mph @ 5800rpm. Fuel supply for the 150hp Yamaha comes via a 200-litre fuel tank. At 4000rpm and 28.5mph on the GPS, fuel burn was 26lph giving it a cruise range of 214 nautical miles. At a trolling speed of 8mph or 7 knots and 1500rpm, the fuel burn was down to 4.6lph.

With the Hyundai SeasAll D170, the XP 716 achieved a top speed of 37.4mph @ 3800rpm burning 32.0lph. At 1500rpm the XP 716 is doing 8mph or 7 knots using 5.0lph – almost identical to the Yamaha. At 3000rpm the diesel will achieve 28.0mph and use 18.0Lph – 8 lph less than the Yamaha. However at 28mph, it will give the 716 a cruise range of 280 nautical miles.

Though it is a slightly bigger boat than the 676, the 716 has a slightly smaller fuel tank at 180L, largely due to the fact of the engine taking up space underneath the floor. But with the exceptional economy of the diesel, it’s no real issue.

On our test day aboard the XP 716, we experienced some fairly typical Auckland conditions, with an incoming tide and wind presenting some rough waters on our way from Half Moon Bay to Motuhie Island. With the extra weight of the diesel inboard, and the slightly longer hull length, the ride was great. It pushed through the chop very easily and had a very solid feel when underway.

It was reasonably easy to trim and with a cross wind, the trim tabs are a must.

As this brand new package was the first Hyundai install for Southern Boats, there was still a little bit of work to do quieting the engine at idle (every alloy boat is different and suffer from different harmonics.). However underway the noise wasn’t overly obtrusive and two of us were able to converse easily enough at cruise.

The diesel option is considerably more expensive to purchase, with a difference of around $30,000 in the base prices. Packages for the XF 676 start at $99,990 with a Yamaha 150hp ($25,500) four-stroke outboard.  Packages for the XP 716 with the Hyundai SeasAll D170 start from $129,995. As tested this rig was $145,995 (Engine and Bravo drive costing $42,600.)

The Winner

So is there a clear winner deciding between a diesel stern drive and a four-stroke outboard of similar powers? Well it’s a hard call. It largely depends on what your preference is and where you do the majority of your boating. If you spend a lot of time on the water, and do 50 plus hours a year, a diesel stern drive might be a better option. You’ll also find, if you fuel up on the water, many marina’s and wharfs around the country still only have diesel available at the pump. You probably need to factor in the cost of petrol v diesel, although ultimately that’s a small cost for your boating enjoyment.

There is obviously a huge difference in vessel range; a 150hp Yamaha four-stroke powered boat has a range of 214 nautical miles at 28mph. The Hyundai SeasAll D170 however will allow you to go 280 nautical miles at the same speed, which is quite a significant difference.

Overall, both engine packages have their good and bad points, it’s really just a matter of what suits you best. For me, I’d happily have either.

Specifications

  • Make &Model: Southern XP 716
  • Manufacturer: Southern Boats                    
  • Price as tested: $145,995
  • Type: Hardtop
  • Construction: Aluminium                
  • LOA: 7.10m
  • Beam: 2.45m
  • Deadrise: 20 degree      
  • Trailerable weight: 2000kg
  • Test Power:   170hp Hyundai SeasAll diesel
  • Power Options: Outboard or diesel sterndrive
  • HP Range: 170-225hp
  • Fuel capacity: 180L
  • Trailer: Custom

Yamaha 150Hp Four-stroke

rpm

MPH

L/h

1000

5.0

3.3

1500

8.0

4.6

2000

9.5

7.2

2500

11.5

11.5

3000

15.5

15.7

3500

23.0

20.6

4000

28.5

26.0

4500

31.0

31.7

5000

35.5

44.8

5500

   39.0

58.0

5800

42.0

63.7

Hyundai SeasAll D170

Rpm

790

MPH
3.6

L/h

1.5

1000

5.7

2.1

1500

8.0

5.0

2000

11.5

9.7

2500

20.4

14.0

3000

28.0

18.0

3500

33.3

27.7

3800

37.4

32.0

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