Kona 18 Jet

Andy Adams

A fast, no nonsense muscle boat.

This month, for our powerboat series, we’ll cover a pure “muscle” boat equipped with the Chevrolet 454 jet drive. This is a high performance power plant by any standards. Installed on the Kona 18 it might not make a lot of sense to some.

But this is a speed boat designed specifically for calm lakes and favourable weather, and not particularly for cruising or skiing. The Kona has speed in reserve.

The Kona is an 18-footer with shallow draft and a slight V-bottom with lift strakes. The deck is long, the passenger area small, and the engine compartment stuffed. Grey metal flake in several tones adorned the test boat along with a mid-grey carpet and pearl-grey upholstery. The engine is covered by a molded hatch that swings up and sideways. Even the engine compartment has a grey-carpeted floor.

Although I personally find metal flake finishes a bit gaudy, the Kona is more subdued and tasteful than most. Overall, it’s a sleek and purposeful looking muscle boat.

There is no windscreen to mar the Kona’s lines and this supports the image of performance, but I feel a windscreen is needed. Even a reverse flow spoiler would help. At speeds near 70mph the wind in your face makes breathing and seeing difficult or even dangerous.

The seats are low-back “buckets” with curved backs that wrap around you. This holds driver and passengers in place and is essential in this type of boat. But the seat cushions are not as thick as they could be. The Kona’s high speed calls for extra padding.

In the stern there are two seats separated by a cooler with a padded top that can be used as an extra seat in a pinch, but really it is a four-place boat. Swivel seats are optional but higher up.

There is no floor in the Kona. The carpet lies over the boat’s bottom and the heavy hull stringers are plainly visible. That’s not to say that the boat isn’t well-finished. There are no visible ragged edges, everything is securely fastened, and no corners are cut. It has the look of quality right through.

Your gaze is met by finned aluminum valve covers, chrome-top air-cleaner and flame-arrestor, aluminum manifolds, and all the other glitter this type of boat presents. The engine is a 454-cu-in Chevrolet with four-bolt mains and the other good stuff. Built by Panther in California, it’s equipped with a 750-cu-ft/min Holley double carburetor, high-rise intake manifold, and Mallory dual-point distributor. It’s rated at 405 horsepower.

All that power is funnelled through a Berkeley 12JE jet pump equipped with an A-impeller, which is aluminum. This pump has a small rudder for low-speed steering that works fairly well but it does not have a trim device for altering the angle of thrust. None seems to be needed but there may be more performance potential with one.

The boat really performs. More than 400 horsepower should be plenty for any 18-footer, but while many boats can manage speeds up to 50mph, getting beyond that takes a lot more than just horsepower. The Kona topped out at 67 mph on radar at a relatively relaxed 4,800 rpm. That’s flying on water with an engine that’s not completely limbered up. A few more hours on the engine might make it push 70.

One problem with a fast boat is that top speed often comes at a sacrifice in acceleration. If the boat is propped to accelerate, then it usually has a limited top end. The Kona not only hits nearly 70 but it accelerates well (0-67 mph was electronically timed at 8.59 seconds). That looks like 0-60 in less than 8 seconds, which is about the best a Corvette will do.

When the throttle is opened the revs immediately shoot up to 4,800 and hold there for an instant, then drop as the engine loads up and climb again to maximum, all in less time than most would expect. The Kona planes so easily it was difficult to time for this. The bow never comes up very high and stern doesn’t dig down.

The driving position is comfortable but a bit higher than I would have liked. The Kona is so shallow you sometimes feel there isn’t much boat around you. I would feel more secure a couple of inches lower. The wheel is a small-diameter black-foam design with good grip even when wet, and feels solid. The gear shift mounts on the left side and the throttle is a foot pedal on the floor.

Two stout springs on the accelerator pedal insure that the engine returns to idle when you lift your foot. There isn’t much travel to the pedal and the springs are a little difficult to get used to. Also, the steering has only about 11/4 turns lock to lock. This is a feature I don’t like. Slower ratios are easier to control at high speeds and accommodate some degree of heavy-handedness.

Monitoring engine gauges could be easier if they were positioned more in the driver’s line of sight. This is especially true for tachometer and oil pressure gauges, which are critical to the longevity of this type of engine. Our test boat was not fitted with a speedometer, but this now is standard. The instruments are complete and useful, but the glass faces glare at times and make reading difficult.

Trick-skiing is out for the jet Kona because it hasn’t got a big-enough wake, but with its standard ski bar it would be good for skilled slalom skiers. The boat won’t plane much below 2,500 rpm. It is happiest at 3,000 rpm or 37 mph, which is too fast for most slalom skiers. At 2,500 rpm the speed drops to 27 mph, which is a bit slow. The adjustment is touchy here and the serious skier will want a different impeller in the Berkeley to get the pull at ski speeds.

Anyone who thinks jets are hard on fuel is in for a surprise. At 3,000 rpm and 37 mph the Kona travels 5 miles per gallon, which is quite respectable. That’s cruising in a big rush, too. Virtually every jet driver I’ve met runs with fast, hard jabs at the throttle, going from medium to wide open to idle between waves. This ruins fuel economy and is hard on the engine besides being unnecessary. Gas-guzzling, then, is up to the driver.

You won’t run this one wide open all day; it’s too fast for that. Handling the Kona should be fun on the smaller lakes and rivers in eastern Canada. The V is not sharp enough to be great in big water, and the speeds would give driver and passengers a beating. But it has a fairly smooth ride that is less affected by waves or winds than some other fast boats are.

Jet thrust creating no sideways torque, the Kona is easy to steer at all speeds. Even at idle it always tracks straight.

All in all, the Kona 18 jet is a very fast boat, easily handled, not bad with gas, and if the $12,000 (1978) price tag seems high, try going as fast for less. And there’s a bonus: The boat isn’t noisy!

Originally published in Canadian Yachting’s October 1978 issue.

Specifications:
Length: 18 feet
Beam: 7 feet
Depth: 30 in.
Draft: 12 in.
Seats: 4
Engine: Chevrolet 454 by Panther.
Jet pump: Berkeley 12JE
Maximum rated hp: 405
Deadrise at transom: 14 degrees
Fuel Capacity: 20 gallons

Performance:
Speeds: 67 mph @ 4800 rpm
53.5 mph @ 4000 rpm
37 mph @ 3000 rpm
27 mph @ 2500 rpm
9 mph @ 2000 rpm
5 mph @ idle
Acceleration: 0-67 mph (max): 8.59 sec
0 – bare plane: 1.79 sec
Fuel economy: 4.82 mpg@ 3000 rpm

Photo Captions:
Photo 1 – The Konas lines are clean, sleek and functional as those of performance boats should be.
Photo 2 – At speeds of nearly 70mph the wind in your face makes breathing and seeing difficult.
Photo 3 – The stuffed engine compartment has a Chevrolet 454 supplied by Panther.
Photo 4 – The instrument panel contains tach, oil, water, voltage and fuel gauges.