Seabreaker 6.3m Cuddy

It has been a long time coming, but Hamilton Marine is back in the boat building game with the launch of its all-new 6.3m jet-powered cuddy-cabin. Jetset's Paul Smith enjoyed an exclusive invitation to step aboard.

Seabreaker 6.3m Cuddy
Seabreaker 6.3m Cuddy

As New Zealand's first and largest manufacturer of marine jet propulsion systems, CWF Hamilton & Co. Ltd have long recognised that commercial success lies in the wider marine market as opposed to the river boating sector where, of course, it is dominant.

Since the mid-1960s the company has produced craft designed for coastal sea going applications, both commercial and recreational. In the last decade the company has focussed on the production and marketing of its jet propulsion systems rather than boat building. They have also lobbied boat builders in New Zealand and offshore to offer jet propulsion as an alternative to outboard and/or stern/shaft drive specifications.

While this strategy has indeed been and continues to be successful, Hamilton Marine regularly receives customer inquiries for "turn key" packages for jet boats suitable for recreational coastal fishing and dive work. Given that the company is well geared up for the construction of aluminium river jet boats, it seemed logical to build on this expertise and offer their own product to this rapidly expanding market. In the 1970s the company had some success with their 18"4' GRP cabin boat marketed as the Jet 83. This boat exhibited good handling characteristics in a variety of water conditions and, since most were powered by V8/3 stage jet combinations, provided great performance.

The J83 gained a solid reputation and spawned a number of siblings that, in various forms from a number of manufacturers, made their own success in the late 1970s and 1980s.

Drawing on this heritage, Hamilton's took the hull lines of the Grandfather J83, and commissioned Richard McBride of McBride Design to rejuvenate the design to meet contemporary requirements.

McBride stretched the hull length by a metre or so to create a gentle stem curve and to provide the appropriate gunnel heights required. This growth process was also necessary to achieve the compound curvature of the hull bottom when constructed in alloy which was easily achieved in the shorter J83 being of GRP construction.

A strong and rigid hull construction was achieved by a matrix of 4mm longitudinal girders and supported by 4mm frames. The girders are welded to the 4mm hull bottom plates. The frames were glued and insulated from the bottom plates in an effort to reduce noise, vibration and harshness while still providing excellent rigidity and hull reinforcement.

The hull topsides, transom, bulkheads and decks are all in 4mm alloy while the 3mm chequerplate alloy cockpit floors are fully welded, so too is the curved front of the cuddy cabin. A robust alloy extrusion forms the gunwhale rubbing strip which provides protection from light impacts.

Given the highly competitive recreational fishing and diving market at which the Seabreaker 6.3 is aimed, a good deal of thought has gone into the layout of this new boat.

The emphasis is on a day boat that provides a spacious cockpit for fishing and diving, while the cuddy cabin provides a measure of protection should the weather cut up rough. The boat does not pretend to be a cruiser but rather a well appointed utility boat.

An inspection from the bow of the Seabreaker 6.3 reveals a deep anchor locker to starboard of the fairlead with its own hinging cover. Anchoring is simple with a solid anchor cleat, while access to the foredeck is good via a large hatch in the cuddy. A chequerplate raised step assists in this regard.

The cabin is fully lined and has a floor to ceiling height of 1.5 metres giving ample sitting headroom. The overall length of the cuddy at 1.94 metres allows for two short squabs with storage under. The squabs will seat two adults on each or provide a bunk for a child. The width of 2.28 metres allows plenty of legroom and space for a portapotty if required. The cuddy is separated from the cockpit by a lockable alloy rollaway door. A notable feature is the provision of two removable, flotation devices which double as back rests and which are upholstered in rescue orange with rope grab handles. The fire extinguisher and light complete this area.

The helm station is mounted on the starboard side of the cabin bulkhead. A basic instrument cluster includes a tachometer, engine coolant temperature and fuel gauges. These are supplemented with a six-unit gang switch and warning lights for oil pressure and battery charging. An auto bilge pump is fitted, as too are nav lights. Morse controls operate the forward/reverse bucket and throttle, both of which fall easily to hand. The steering nozzle is controlled by a Morse cable that is very light, giving one full turn of the small diameter wheel from lock to lock.

A large flat area atop the cabin bulkhead and behind the windscreen has a 50mm raised lip for storage of light articles. There is plenty of space for either bracket or flush mounting of electronic aids. An adjustable pedestal helm seat is complimented by a chequerplate footrest welded to the cabin bulkhead for comfort when seated. A similar passenger seat is equipped with a stainless steel grab rail and similar footrest. Both seats are well placed to allow the driver and passenger to stand while underway.

The Taylor Made toughened glass windscreen with fitted grab rail gives good protection while the bimini cover and clears attach to the stainless steel rocket launcher which provides a useful two metres of headroom from the cockpit floor.

The internal dimensions of the cockpit confirm the feeling of spaciousness - the length from the transom to the cabin bulkhead is 3.45 metres and the internal width measures 2.070 metres. The gunwhale height is 650mm from the cockpit floor. The alloy engine cover measures just over 1 metre in length from the transom and is 865mm wide. Its height of 565mm means it is ideal as a base for a custom bait station for fishing.

The cockpit floor is fitted with SoPac access hatches providing access to an underfloor dry locker between the pedestal seats and just forward of the 125-litre alloy underfloor fuel tank. Another locker forward of the engine cover gives access to the battery.

A large plastic double fishbin has two upholstered squabs to match the rest of the trim and provides additional seating. It can be moved around the cockpit at will. Long side pockets allow for paddles, rods, intake rake and/or gaff storage, and a shelf extension for the auxiliary tote tank is situated under the port rear deck, close to the transom mounted auxiliary bracket. The side decks are fitted with six-rod holders and are wide enough to sit on while fishing.

An interesting feature is a wash down hose and tap that uses a water take-off from the high-pressure side of the jet unit. The floor is self-draining with transom scuppers on each side of the engine box. The whole of the cockpit with the exception of the floors is painted in multifleck paint and finished in clear lacquer.

A large alloy and timber slat transom mounted boarding platform is a useful feature for both fishing and diving activities while providing a valuable source of impact protection for the jet unit.

The hull topsides, deck and cabin top are nicely painted while the chine stripes accentuate the boat's length.

Since the focus of this example of the Seabreaker 6.3 is on economical family boating, a small lightweight turbo diesel engine was selected to drive the Hamilton 212 jet unit. Hamilton's were also keen to evaluate the overall efficiencies of this type of engine in a jet drive system. The Steyr marine diesel chosen is an in-line four cylinder, four-stroke design displacing 2133cc. It features electronic fuel injection, is turbocharged and intercooled and, since it uses extensive aluminium alloys in its construction, it is quite light at an overall weight of 258kg.

The engine is rated at 120kW (164HP) at 3700-4000rpm and produces its maximum torque rating of 330 Nm at 2300 rpm. The engine is coupled to the jet using a Centa torsionally resilient coupling to maximise smooth power delivery while ensuring a compact installation. The jet has been fitted with a stainless steel impeller rated at 2.2 kW to match the power and torque delivery of this engine.

Considering the relatively small capacity of the engine, the output is quite good. The lightweight is evident when the boat is at rest with the chines at the transom just touching the water.

Performance and handling
On paper, considering the power output of the small diesel and the size of this boat, our performance expectations were not high. Once in the water however, we were surprised. Our test on Lyttelton Harbour where the water was being whipped up by a building north westerly and a half metre chop would test the dryness of the design.

Clear of the 5 knot restricted area the throttle was opened and the Seabreaker 6.3 effortlessly climbed on to the plane. There was a little evidence of turbo lag until the engine reached 2500 rpm, whereupon it came on strong, delivering a pleasing surge of power. The boat quickly settled into its cruising sweet spot with 3250rpm on the tachometer.

At this speed, engine noise was not overly intrusive with the sound deadening material of the engine box and the large capacity transom-mounted muffler doing their work well. With half a tank of fuel and three adults aboard, the Seabreaker 6.3 was moderately loaded with GPS indicating a speed of around 23 knots.

The chines did a good job of deflecting water down and away from the boat while underway, and only a small amount of windblown spray found its way on to the screen courtesy of the gusty northwester. The boat could be pushed hard into, and with, the chop without fear of broaching and with little pounding, indicating the balance of the hull is such it does not demand the use of trim tabs. The boat responded quickly to the light helm at all speeds making for a relaxed drive. It soon became apparent that the Seabreaker 6.3 could easily handle substantially greater power for better top end performance. However, the performance of the little turbo diesel was adequate for general use. The advantages in using such an engine in this application are obvious; better fuel economy and less engine wear.

The advantages jet propulsion brings to recreational boating are significant - shallow draught, no dangerous propeller or underhull appendages to snag or damage, excellent manoeuvrability at all speeds, and reduced maintenance costs. When diesel engines are used in conjunction with a jet and their attendant advantages of economy, longevity and safety, a powerful argument is formed in favour of jet propulsion.

The package is well finished and was presented on a multi-roller, galvanised steel and tandem axle trailer with hydraulic override disc brakes on the front axle.

With an all-up weight of 1740kg on the trailer, it was capably towed behind my Mitsubishi Pajero turbo diesel and the whole rig pulled up safe and true in a panic stop from 60 km/h.

Hull: Seabreaker 6.3
Builder: Hamilton Marine
Designer: McBride Design & Hamilton Jet
Type: Cuddy
Construction: Aluminium
LOA: 6.3 metres (hull only), 7.0 metres inc. boarding platform
Beam: 2.420 metres
Chine Beam: 2.0 metres
Deadrise: 20 degrees
Freeboard: 800mm at transom
Trailerable Weight: 1740kg, full fuel
Fuel Capacity: 125 litres approx
Options (as tested): Boarding platform, auxiliary bracket, bimini cover, rocket launcher, fish bins
Engine: Steyr 164 Marine Diesel
Capacity: 2133cc
Weight: 258kg
Output: 120kW at crankshaft @ 4000 rpm (Manufacturer's claim); 107kW as tested @ 3650 rpm
Jet: Hamilton Jet 212
Type: Single stage high volume, mixed flow
Impeller: S/S, 2.2kW
Nozzle: J/T style, 110mm diameter
Price as tested: $84,000.00 inc. GST

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