HamiltonJet 161A

By: Paul Smith

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Although most production from Christchurch’s CWF Hamilton & Co Ltd is large, marine propulsion applications for off-shore clients, the company has never forgotten its river boating roots. This is evident in its latest recreational jet boat.

HamiltonJet 161A
HamiltonJet 161A

The smallest boat in the HamiltonJet range is the venerable HJ212 – which also happens to be the company’s best-selling model. But that may change with the newly-released HamiltonJet 161A.

At five metres in hull length, the 161A has evolved from its predecessor (the 151XL), though its true DNA can be traced back to the Jet 52 of the 1970s – the boat that made history in the hands of Jon Hamilton and Sir Edmund Hillary on the waters of the Ganges River in 1977.

A legacy of the international jet boating expeditions completed by HamiltonJet boats over the years is the expectation that they are built for ‘rugged’ use. Like the Range Rover, HamiltonJet boats are capable of performing in far harsher conditions than most of their owners will ever subject them to.

Construction and design
The new 161 hulls are constructed in 5083 marine grade alloy plate, cut and welded in place on a steel jig to ensure consistency of shape and form. The delta keel plate is folded from 10mm thick plate (12 mm is an extra cost option for the more adventurous), while the hull’s outer bottoms are formed in 5mm plate. Topsides and transom are 3mm.

The basic hull is reinforced with four longitudinal bearers in 4mm while the stem has a 10mm x 40mm reinforcement. Hull plates in front of the keel plate are reinforced with 6mm x 100mm doublers, while four planing strakes (either side of the keel) are formed from 3mm angle and stitch-welded to the hull bottom.

A GRP deck is bonded and riveted to the alloy hull, with the join covered by the rubber gunwale beading. The use of the GRP deck not only streamlines production, but also allows a nicer, smoother finish than is otherwise economically available in fabricated alloy.

The design of the HamiltonJet 161A closely follows the slightly shorter 151A, except that the extra waterline length provides for a nice, gradual stemline that gives a smoother ride in rougher water. A 1.90m beam keeps the proportions right and the moderate deadrise of 16 degrees is a good compromise for shallow water operation while still giving good directional ability. The use of four planing strakes per side provides superior lateral adhesion even in the tightest of turns.

Cockpits can be configured to suit customer preferences, although most seem to prefer the ability to walk around the engine box to access the transom. This means the use of an extended double bucket-style rear seat in addition to two bucket-style front seats.

Location of the fuel tank is also optional – an under-floor tank with a capacity of around 115 litres allows for additional storage in the rear seat base, but if a slightly aft longitudinal centre of gravity is preferred, the fuel tank can be located under the rear seat and immediately for’d of the engine.

The portside helm is nicely located, with the steering boss extension placing the wheel comfortably at hand. Engine instruments are positioned immediately ahead of the driver without obstruction. The forward and reverse control actuator is found on the port coaming. A Morse foot throttle is also well placed for comfort. 

On the cockpit’s starboard side, the dashboard features a deep, lined open-front storage locker. The centre of the dashboard is cut away and a solid step provides for deck access. With the trend toward higher sided boats, access to and from the cockpit is more difficult due to the greater height between the cockpit sole and the top of the windscreen. A dashboard-mounted step assists greatly in this regard.

Engine covers are formed in moulded GRP and are easily removed for full access to the engine and waterjet. A high capacity auto bilge pump and a manually-operated electric bilge pump
are standard.

A notable optional extra is a boarding platform mounted on the transom. In addition to being really useful for swimmers and waterskiers, the alloy-framed, timber-slatted platform provides some impact protection to the waterjet when manoeuvring in confined areas and when trailering.

Fit and finish
Since the GRP deck can be attached to the hull after all of the instrumentation, steering and forward/reverse controls have been installed, it is easier to achieve a neat finish. The standard specification provides for a durable and easily cleaned interior, with the cockpit sides and plywood floors finished in speckled paint. A moulded GRP front sole section includes the footrest and has a non-slip finish.

For those wanting a ‘softer’ feel, the cockpit can be trimmed in marine carpet. This also reduces internal noise levels. One of vessels we reviewed was optioned with stainless steel bowrails, pop-up stainless steel cleats and custom paint graphics to match its tow vehicle. These features add to the individuality of the boat.

Performance and handling
Hamilton Marine provided three examples of the 161A for our river-based evaluation. The first was a stock standard, factory spec base model vessel fitted with a 300hp MarinePower V8 engine. Based on the 350ci (5.7-litre) Chevrolet small-block engine, it features multi-point electronic fuel injection and ignition.

The engine was close-coupled to the HamiltonJet HJ212 waterjet fitted with a 2.4kW ‘turbo’ style impeller.

The second vessel had not seen a river until our test day. It was fitted with a customer-supplied Chevrolet ‘crate’ motor that had been marinised. This engine – the ZZ383, a 6.3-litre V8 – produces 425hp at 5200rpm. It has a specially prepared carburettor and uses the GM HEI electronic ignition system. It was also close-coupled to a HamiltonJet HJ 212 waterjet fitted with a 2.4kW ‘turbo’ style impeller.

The third vessel had been returned to the factory for repairs and maintenance after completing a grueling South Island adventure. This boat had been up-spec’d with a MarinePower LQ9 S/C (supercharged) engine. Based on the Generation 3 version of the 6.0 litre General Motors V8 engine, it features electronic engine management in addition to a factory fitted supercharger and intercooler, and provides an output of 450hp at 4600rpm. The engine was close-coupled to a HamiltonJet HJ 212 waterjet fitted with a coarser 3.4kW ‘turbo’ style impeller.

While the 161A would likely perform quite satisfactorily with a four-litre engine, the larger and more powerful engines are better to drive the standard 2.4kW rated impellers (or larger). Accordingly, boats so fitted are better able to carry greater payloads and, under cruising conditions, remain comparatively economical.

For almost every practical recreational application, the standard issue 300hp engine is more than satisfactory. The table (on p38) indicates the rpm/boat speed evaluation for each of the power systems. Where the same impeller is used, the additional horsepower generated by the larger engine reflects in a higher top speed and greater mid-range acceleration.

The supercharged engine delivers a markedly improved performance level across the range simply because it generates sufficient power to swing the coarser impeller. In every respect the supercharged engine out-performs the others and when cruising off boost, fuel efficiency would be comparable, if not better, than the naturally-aspirated engines.

The price penalty at the pump only becomes evident when the throttle of this engine is subjected to plenty of jandal. Unfortunately, such is the rush when this boat is given its head, that the temptation to repeat the experience is compulsive and therefore may be rather expensive.

The other interesting conclusion that can be drawn from the performance table is that, given sufficient input power, the HJ 212 waterjet is more than capable of delivering scintillating performance levels and more importantly, does so at comparatively modest engine speeds, especially with the coarser-pitched impeller.

For convenience, I’ve included the relative input horsepower (imperial) absorbed by the waterjet at each engine rpm segment.

Each of the boats was subjected to a minimum planing speed test. The engine rpm and boat speed across ground were noted just as the boat began to fall off the plane. Minimum boat speed was affected by nozzle trim setting, engine weight and fuel tank positions.

We were able to put each of the boats through a number of manoeuvres in a variety of river conditions, and we concluded the performance and handling of the boat is predictable and safe. The hull design and execution has a long history of performance and its pedigree is impeccable.

The verdict
The HamiltonJet 161A may be a recent offering, but the styling makes it instantly recognisable as a Hamilton product. Some may say the look of the boat is dated – it is after all, almost identical to the 151A that was first released back in 1983. But therein lies the secret to its branding success and the reason why HamiltonJet products command premium resale values. As they say: "If it ain’t broke, don’t fix it!"

Personally, I like the look of the boat and this 161A configuration is the most attractively proportioned. There is no denying the fact you will pay a premium for the brand as a ‘factory finished’ boat, but this is reflected in the high re-sale value and the on-going demand for the boats in the HamiltonJet range.

(Price from $72,835 inc GST, depending on specs)

LOA:   5.0m (16’5")
Beam:   1.9m
Deadrise:   16º
Construction:     5083 marine alloy
Deck:  Moulded GRP
Propulsion:     HamiltonJet HJ 212  waterjet, 2.4kW  ‘turbo’ style impeller
Engine:  Standard 300hp V8  petrol

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