SPLASH, DASH, AND A BIT OF BOOST —

THE LIFE OF ADAM WILTON

Most of us started our love affair with V8s with tyres rotating on tarmac, but Adam Wilton started with hulls hitting water. A man with a passion for fast boats and LS engines, Adam started working for a North Island boatbuilding business at 18 years old, building small and large boats, ranging from fishing boats to touring boats to jet and race machines. Of course, the inevitable happened; a couple of years later, he had built a boat for himself in his spare time — not just a little fishing dinghy but a 5.3m jetboat powered by a Lexus V8. A string of personal boats followed with jet-ski engines, a Nissan V6 turbo, a ZZ383 Chev crate engine, and even a brand-new supercharged 3.8 Buick V6 that Adam spotted one day sitting at a Holden dealership in Tauranga.

An interesting side story is that, while Adam was building the first boat, he got impatient with seeing his Lexus engine sitting on a pallet each day, so took a tape measure to it; compared it with his Nissan Navara engine bay; thought he could make it work; and, hey presto, two weeks later, the V8 was being tested in the little Japanese ute. It was a bit of an expensive engine test, though, as it cost Adam many rear tyres and actually managed some 13-second quarter-mile runs before eventually making its way into the jetboat!

In 2007, when the global financial crunch hit and boat sales started dropping in the North Island, Adam moved to Rangiora, just north of Christchurch, working for the same company but with a different demographic market. It was here that he got interested in remote-controlled quarter-scale jetboats. These are powered by miniature 1.8–2.0ci gas two-stroke marine engines complete with water-cooled manifold, head, and exhaust and coupled to a little jet unit that is so cute you could sit it on the mantelpiece as art.

Designed in Aussie, the scaled-down jet unit is just like a big one, with water-lubricated rear bearing, twin front main-shaft bearings, carbon ceramic water seal, and stainless-steel impellers. Adam invested time designing his own quarter-scale hull based on a V8 jet-sprint boat and built his first one in 2011. Then, when he posted a pretty average video on YouTube, his phone started ringing. He had so many enquiries, he realized that he needed to CAD-model the boat and start building them in his home garage in his spare weekends.

If you’ve never seen these boats, go to YouTube and search: ‘1/4 scale Jettec’. These are for committed hobbyists, as they are a serious piece of kit and easily reach 37-plus miles per hour in just 1.5 seconds! To date, Adam’s built more than 70 of these little boats, mostly for overseas clients, and shipped them to many countries.

After seeing the build quality of the little boats, a guy in Canterbury asked Adam if he could build him a full-scale jetboat, and that was basically the start of Adam’s Jettec business: starting with a few 3m two-seater boats and then rapidly progressing to bigger big boats with V8s. Fast forward seven years and Jettec has manufactured more than 90 big boats plus another 20 or more for other companies, and more than 30 aluminium boat and jet-ski trailers.

Rather than focus on the world-class quality and stunning design of Adam’s jetboats, we recently caught up with him to ask about marinizing the engines and modifying the LS engines that are now commonplace in many of his boats. Having originally used various engines, Adam finds the LS ones are now hard to beat, being uber-reliable. That’s not to mention that they are easy to find, easy to get parts for, easy to increase horsepower on, and very compact. The key point, though, is reliability; that’s one of the most important hallmarks of a jetboat engine, as, when it’s not running, you lose all steering and all forward and backwards thrust. Remember, too, when this happens, you’re at the mercy of a fast-flowing river with obstacles such as trees and rocks lining the river banks; you can’t just pull over and stop the way you can in a car.

Most people who buy one of the bigger-hull Jettec boats spec either an LS1, if the budget is tight, or an LS3 for the biggest, baddest, boldest, and more expensive option. Adam has looked at other engines, such as the LSA with a supercharger, but adding 120kg to the normal boat weight of around 850kg doesn’t make sense when there are so many mods available to increase horsepower and torque in naturally aspirated engines. Even a naturally aspirated LS1 with a more efficient cam gives good, honest, and cheap horsepower, and it’s hard to beat gaining 80hp by investing in a cam, springs, and labour for around $1400.

Adam has also installed many engines with a

HAVING ORIGINALLY USED VARIOUS ENGINES, ADAM FINDS THE LS ONES ARE NOW HARD TO BEAT,

single-turbo over the years, but one of his recent large boats has a 2014 Camaro LS3 engine fitted with twin BorgWarner 60/68 turbos, specifically tuned for the rpm and boost that Adam is running with this motor. Twin large water-to-air intercoolers make sure the LS is getting plenty of cold air, and both the pre- and post-turbo pipework is water cooled to help keep external temps down.

The turbos run twin 45mm external wastegates and the turbo housing has been ceramic coated by Elite Powder Coaters of Christchurch, again to keep external temperatures down and the heat inside the turbos. To keep reliability high, modifications are pretty quiet on this engine compared with on some of the earth shakers we’ve seen on the pages of NZV8. However, even running on a low boost of 8psi with stock bottom end and aftermarket camshaft valve springs, this combo is giving decent reliable power and will save the conrods and pistons, which are known to be the weakest link of an LS when people get carried away turning the boost up.

Over the years, Adam has found that running a high-compression engine with a turbo works well, as it already makes good power down low before boost comes on, but this does put a lot more strain on an engine that was never designed to have boost. Matching the correct-sized turbo and wastegate is very important, and the engine tune

THESE MANIFOLDS LOOK LIKE A PIECE OF ART YOU COULD DISPLAY IN YOUR FOYER

is key to keeping it all in one piece.

Once the boat is up and running, the motor doesn’t get much rest, being constantly under load, working hard all the time — kinda like driving your car up an endless hill in top gear with your jandal hard on the throttle. Even at 3000rpm, the engine is working very hard in comparison with how it would in a car, so the whole drivetrain needs to be super durable to handle the constant stress of all the components.

The 415ci stroked LS3 in the blue boat is an interesting engine, as it was purchased by Jettec from Mast Motorsports in the US and shipped over. It was dynoed in the US at 560hp and 580ft·lb at 5400rpm, which most readers will know is a tricky set of three numbers to get lined up, as it’s easy to get high horsepower at high revs but normally the torque drops off, which is less than desirable for a jetboat. Adam runs the LS engines on either a modified factory ECU and loom or a stand-alone aftermarket ECU like a New Zealand–made Link.

Obviously, the boat can’t be put on a dyno to set up the ECU, so initial tuning is dialled in on the trailer backed in the water using up to 50 per cent fuel ratios. Using headphones, Adam listens for engine knock, gets it close, then runs the boat on the river with the jet unit acting like a dyno for the final tuning.

The cooling of a V8 in a boat is interesting, as there is no airflow over the sump as in a car, but the bottom of the hull is running in cool water, making the temperature of the engine bay cooler than a car bay most of the time. Engine cooling is still required though, and there are a couple of options: a closed heat-exchanger with copper pipes, recirculating the engine water around the outside of the pipes, or an open-loop cooling system with a water mixer that mixes the water you are boating in and again thermostatically regulates how much is recirculated. Most people use an open cooling system, as it is cheaper, and most of the time customers are running their boat in fresh, clean water. Some customers also choose to have an oil cooler, which is thermostatically controlled in a similar fashion.

Water-jacketed exhaust manifolds made from thick-walled cast alloy cool down the exhaust temperatures with the water running around the outside of the exhaust. Not only do these manifolds look like a piece of art you could display in your foyer, but they are also cleverly designed so that the water exits the downside of the manifold, giving it no chance of getting back into the engine. On the propulsion side of things, all that horsepower has to be converted into forward thrust, and Jettec chooses to run different jet units from Hamilton Jet, Scott Waterjet, Southern Jet, and Flo Pro depending on the drivetrain spec, size of boat, and what the boat will be mostly used for.

Some jet units can run one, two, or three impellers, but the most common is two, with pitch and nozzle diameter determined by the expected horsepower of the engine. It’s super important to get this right to avoid slippage, especially in high-speed corners such as a fast U-turn for which you need lots of grip and control of the boat, as the unit needs to be pumping water for that control to be achieved. The heart of the jet unit is the impellers, their clearance tolerances, and their condition, so, if the boat is run in shallow gravel beds or across sand bars, the impeller leading edges will wear quickly and become dull and inefficient. Pumping sand also increases the wear to impeller clearance, causing cavitation and loss of performance.

Jet units are energy-sucking contraptions, and, due to the water drag, a jet unit actually tries to stall the moment that you take your foot off the gas — similar to putting your foot hard on the brake in a car without depressing the clutch. This is most likely to happen with quick off-throttle moments, such as when you are cruising at 3000–4000rpm and suddenly back off the gas — perhaps, for example, when you aren’t sure which river channel to take. For this reason, the engine has to be set up with a high idle, often called the ‘idle base duty cycle’, to keep the engine at highenough rpm to avoid a dangerous cut-out. When it comes to reversing, there is no clutch, there is no gearbox, and there are no brakes — which pretty much describes an old Mazda rally car I had! — but there is a mechanical ‘reverse bucket’, which is simply a curved bucket that comes down over the jet nozzle and directs water under the boat against the river flow for a neutral position when partially down, or for backwards thrust when the bucket fully covers the nozzle. This makes good use of Newton’s third law of motion — every action has an equal and opposite reaction — and is basically the same as the reverse thrust felt when holding a powerful fire hose. On the end of the jet unit, the steering nozzle has tuneable alloy inserts to change the boat’s cruise speeds and engine operating rpm. There is often also a trim nozzle for trimming the front of the boat up or down to get ultimate performance from the hull. Jetboats are more complicated than cars when it comes to drivetrain options, as there is no perfect boat, engine, and jet unit for every boating situation. Different drivetrains and hulls will have

advantages and disadvantages, and no one design will work perfectly in every boat with every driver for every application. Some people want to tow a skier, some are content with cruising up a river with all the family and a picnic lunch on board, some want to be able to keep going with a grille full of stones on thin water, and some want to carry a load of venison back from a successful weekend hunting. Adam works hard with each owner to determine what they want to do with their boat and what performance they want, then selects the hull, the engine, and the jet unit to achieve this.

You can see that Adam’s definitely a true, diedin-the-wool V8 fan with a passion for world-class engineering and detail, and a genuine guy who loves what he’s doing for a living. He’s definitely working with a different set of parameters and different solutions for high-performance V8s than we are used to with four-wheeled vehicles. He’s not completely one-eyed, though; he also has his own four-wheel project: a 1967 Plymouth Belvedere wagon with factory 318 V8 that he’s owned for four years, slowly restoring it to look like new again. Adam would like to take this chance to thank Gary and Gareth from Scott Waterjet; Clayton from Southern Jet, for manifold work; Jason from SAS Christchurch, for wiring and tuning the LS engines; and SSS Engineering in Christchurch.