The Personal Watercraft - Growing Up Fast. The Personal Water Craft (PWC), by definition a highly manoeuvrable, light fast boat powered by water jet propulsion and where the crew sit on, rather than in, the craft. Seems like such a simple idea that it could have been around since the beginning of small powered boats, but no, it's a relatively recent invention. In 1968 the Bombardier corporation was going very well with its Ski-Doo brand of snow mobiles. Snowmobiles had revolutionised personal transport in the depths of winter, if you happened to live where there's plenty of snow and ice, like more than half the world's population. But winter is only half the year. What if we could come up with a similar high performance personal vehicle to the snowmobile, but for summer, and to use on the water? That's was Bombardier's thinking back in 1967 when they teamed up with American inventor Clayton Jacobson, who had recently been granted a patent for the Personal Water Craft. The 1968 Sea-Doo was powered by an air-cooled single cylinder 300cc Rotax engine of 13 kW (18HP). Not much power by today's standards, but the craft only weighed around 120 kg, so it was fun to ride with a top speed of about 40 kph (25mph). The 1969 model had a twin cylinder, water-cooled Rotax engine with 19kW (25HP) and a top speed close to 55kph (35 mph). But the world was not yet ready for the PWC, it was not a marketing success and after just two years, production was shelved. For 20 years. In mid 1980's Bombardier considered the market ready for a PWC and the new Sea-Doo models were released in 1988.

1969 Model Sea-Doo

Now powered by a 600cc Rotax twin cylinder water-cooled engine with 55HP, the Sea-Doo was a two seat sit down type PWC with very good performance. This time the PWC was a success and the market took off with several other manufacturers joining the seemingly insatiable demand for PWC's in the 1990's. Before long there were 1, 2 and 3 passenger models. There were entry level, cruising and high performance models and by the end of the 1990's PWC's had grown to be over 3 metres long, weighed nearly 300 kg and had 97kW (130HP) on tap. Top speed could exceed 100 kph (60 mph). However, compared to other internal combustion engine powered transport, they were still quite simple devices. All were powered by 2-stroke engines of 800 to 1000cc, with very few emissions controls, or electronics. But all of that was about to change. Sea-Doo's engine supplier, Rotax had been working on more powerful engines for the increasing trend towards larger PWC's, with more accessories. Rather than build a new larger 2-stroke engine, Rotax chose to go with a large bore, short stroke 4-stroke engine it had been developing for the motorcycle industry, called 4-TEC. The Sea-Doo version has 3 cylinders, 4 valves per cylinder operated by roller rockers from a single overhead camshaft and a counter rotating balance shaft alongside the crank. A bore of 100 mm and stroke of 63.5 mm yields 1494 cc and in naturally aspirated form when first released in 2002, it had 115 kW (155HP). The following year a supercharged version with 138

1968 and 1988 Sea-Doo's

Rotax type 1503 4-TEC - Forged aluminium roller rocker arms incorporating hydraulic valve lash adjusters are good for 8000+ rpm.

kW (185 HP). It utilised an engine driven centrifugal blower providing 35 kPa (5 psi) boost. For 2005 power was increased to 160 kW (215 HP) by raising the boost to 51 kPa (7.5 psi) and adding an intercooler inside the intake manifold. With cool sea water circulating through the intercooler while ever the engine is running, charge air temperatures are greatly reduced. To cater for our ever increasing demand for performance, in 2007 a much larger, external sea-water cooled intercooler was fitted along with an increase in boost to 65 kPa (9.5 psi). Power is now 193 kW (260 HP) at 8000 rpm.

Rotax 1503 4-TEC engine with centrifugal supercharger running at 5.4 times crank speed provides 193 kW (260HP) at 8000 rpm

Intercooler plumbing on a 2010 Supercharged Sea-Doo

The centrifugal supercharger is light and compact, and most importantly it avoids the lag of turbo superchargers thereby giving the instant throttle response demanded by today's customer. Modern high output 4-stroke engines run best at a relatively hot temperature, so just running sea-water through the engine's cooling passages, as was done with the 2-stroke PWC engines, is not the best option. Sea-Doo uses a heat-exchanger inside the ride plate to allow for a closed-loop cooling system. A 50/50 anti-freeze mix in the engine can now run at 87C for best power and emissions without the risk of sand or silt deposits building up in the engine's cooling passages. Sea-Water is used for cooling only in the exhaust system and intercooler. When the craft is stationary with the engine running the ride plate is submerged so there is sea water on all sides to ensure maintaining engine temperature. At planing speeds there is sea water only on the underside of the ride plate, but it is flowing past at boat speed, up to 110 kph (68 mph), so there is plenty of cooling capacity.

PWC's used to have a reputation for being noisy, but that was many years ago. Today they are amongst the quietest of all boats. Sea-Doo uses dual water cooled aluminium mufflers for very quiet operation. Water is injected into the first muffler, dropping the exhaust gas temperature and engine exhaust sufficiently for it to be carried through the exhaust system's rubber hoses

without damage. The water cooling also has the added benefit of keeping the system carbon free and clean (steam cleaned!). Even the largest Sea-Doo PWC is only around 3.5 metres long and 400 kg, so they are easily towed behind almost any car, which sometimes makes them an attractive target for the sort of people who would like to have one, but without paying for it. In the late 1990's Sea-Doo came up with the Digitally Encoded Security System (DESS) to make it very difficult, just about impossible, to operate without the correct key. Each key, actually a lanyard with a rubber cap on the end, has an integrated circuit buried inside containing a long number of which there are several million combinations.

Dual water cooled mufflers keep 260 horses quite

Each Sea-Doo PWC is then programmed to recognise only certain keys, by the dealer. Without a key the craft recognises the ECU will not provide injection and ignition, nor even crank the engine. And hot wiring the starter won't help. Fronting up to your local Sea-Doo dealer wanting a key programmed will also result in some polite but insistent questions to ensure you are the owner or have their permission. Another feature associated with DESS is the Learning Key. A second key is programmed so that the engine's management system will limit the engine's power and the PWC's performance. Most of us would not hand over the key's of our new high powered sports car to someone that has never driven one before and it's the same with a PWC. A 260HP Sea-Doo can accelerate to 100 kph in around 3 seconds and it can do high G turns easily, so the uninitiated could get into trouble quickly. The learning key avoids that possibility and allows new operators to build confidence progressively. In 20 years the humble PWC has gained a lot of performance and comfort including modern technologies like EFI, supercharging and CAN-bus communication between modules, but it was still a largely mechanical transport device. iControl However, beginning with the 2009 models all that's about to change, with a group of technologies called iControl. Starting with 2 models in 2009 and expanding that to 7 models on 2010 iControl uses a series of interconnected electronic modules, via a CAN network to add a lot more features to Sea-Doo PWC's. iControl has 3 main sub-systems -

iS (Intelligent Suspension) iTC (Intelligent Throttle Control) iBR (Intelligent Brake and Reverse)

All of which share common sensors and modules via a CAN network. iS iControl is the first 3 seat PWC with suspension to soften the ride in rough conditions. iS craft have two decks, one fixed to the hull in the conventional manner for keeping the hull water tight, and the moving deck, which has the seats, dash, controls and foot wells, and is suspended above the fixed deck by two large swing arms. Attached to the forward swing arm is a large shock

Sea-Doo Learning Key, reduced level of performance for new operators to safely gain experience

absorber for dampening, a coil spring to support the load and a small hydraulic cylinder under the coil spring for height pre-load adjustment. An electric motor operates a hydraulic pump so the operator can control suspension height on the fly. Removing the moving deck is not difficult, taking about 20 minutes and is required for most maintenance jobs other than simple oil, filter and spark plug changes. The suspension has 150mm (6 inches) of travel providing a very smooth ride. The rider controls the suspension by buttons under their left thumb and a matching bar graph on the dash LCD display. iTC iTC utilises and fly-by-wire throttle in conjunction with a GPS speedo in the dash and the Engine Control Module (ECM). Without any cables or linkages throttle

Moving or suspended deck

Hull with fixed deck in place

Hull with both decks removed showing suspension arms

iS Control buttons

action is very light and can be easily operated with just one finger. iTC also means no more speed or rpm limits by interrupting ignition or injection to make the engine misfire. Now when a speed or rpm limit is exceeded, the throttle is just closed providing very smooth operation. In addition the learning key function is now adjustable. The operator with the normal (full performance) key can now program the learning system to several different speed limits according to the age or skill level of the other riders.

iTC with a GPS also means we can have Cruise Control, but not the same type as on our cars. An iControl Sea-Doo can be set to cruise at your desired speed, but only while you manually hold the throttle open. Once Cruise control is set you can hold the throttle anywhere from 25 to 100% and the speed will not change, but if you let the throttle close, cruise control shuts off. With iTC you can also have different throttle opening rates. A slow opening of the throttle, in relation to how you move the throttle lever is best for touring as it allows fine tuning of your speed. But for outright performance and get there as-fast-as-possible type riding you switch to sport mode where the throttle opens much faster as you move the finger lever. The rider controls which mode to use, by using the mode/set buttons on the handlebar in conjunction with the central LCD instrument display panel. On the Wake models (and optional plug module on others) there are 5 different launch modes the operator can now program in, so the craft's acceleration and speed can be set in advance and duplicated precisely on every run. Very convenient for tow sports like Wake Boarding so you can set the acceleration and top speed to suit the skier. What if you drive under a bridge? What happens to the systems that rely on GPS when you can't get a satellite fix? While this is a situation that does not happen a lot on the water, in does happen, so Sea-Doo iControl models have a back up electronic system that computes speed from throttle opening and rpm, for those few times when GPS is "blind". iBR The iBR system takes the conventional reverse gate (a curved plate that is lowered over the jet pump outlet to redirect the water flow forward) and powers it with a large, pulse-width controlled DC electric motor. An iBR control module interfaces with the other modules onboard

Throttle lever with dual output Hall Effect position sensors

Bosch ECM that interfaces with other modules for boat speed information

Electronic Throttle Actuator

(via CAN), to allow for an automatic neutral, low boat speed control to control your wake in sensitive speed zones, virtual trim system and also functions as a brake. When travelling below 8 kph (5mph), if the rider pulls the reverse lever (on left handlebar), the iBR system will engage reverse gear by lowering the reverse gate. Throttle control remains with the rider. If the boat is travelling above 8 kph (5mph) the electronics will now engage the brake, by using the reverse gate to throw more water forward opposing the speed of the craft. The ECM will also open the throttle to apply more reverse thrust to stop the craft quickly. Throttle control in braking mode is with the ECM, not the rider. The amount of reverse thrust and throttle applied is dependent on boat speed. Higher speeds can use more throttle for more braking action. iBR is the first brake to be fitted to a PWC and it can shorten stopping distances by more than 30m (100 ft). The iBR system can also control boat speed in "no-wake" zones. The rider can dial up a desired speed using the instrument display on the dash and the iBR system will apply the reverse gate and throttle just enough to slow forward speed to your desired setting. iBR also provides an automatic neutral. As soon as you start the engine, the iBR system moves the reverse gate (in about 1 second) to the neutral position. No longer do you need to concerned where your craft is pointed when starting the engine. iBR also provides a virtual trim system. In the first 15 (approx.) degrees of reverse gate movement (from full up) the jet pump nozzle and gate move together. This provides about 15 degrees of variation in the water thrust direction to raise or lower the craft's bow, at

Nozzle and gate fully up, high trim, nose up position

Nozzle and gate at lower end of trim range, boat will be nose down

Neutral position, equal amount of water flow forward and to reverse

Gate fully down in Reverse position, all thrust is to reverse

speed. This can both increase speed and/or provide a smoother ride, depends on water conditions. The humble personal watercraft has now moved into the era where more onboard features are controlled by software than hardware. And with the progress in electronics lately there's likely to more in future. The hulls of all Sea-Doo's until 2008 have been fibreglass (polyester resins with glass fibre reinforcement and a gel-coat outer shell). But even here there is new technology today. The new iControl models feature a closed mould process called LFI (long fibre injection) that uses glass reinforced polyurethanes rather than polyesters. It cures much faster (only a few minutes rather than hours or days) and the closed mould process ensures both inside and outside of the hull are dimensionally accurately. The moulding process is computer controlled to get the speed and material distribution required, and mounting pads for the engine and other hull mounted accessories can be positioned exactly where required. Best of all, the resulting hull is as strong as the old fibreglass version, but 25% lighter, and with no styrene emissions it's better for the environment. The new iControl S3 hull process also allows for some subtle changes that would have been hard to do on the old fibreglass version. Steps in the aft planning surfaces reduce drag and increase performance, while additional spray deflectors near the bow keep more spray down away from the riders when the going is a little rough. The outer surface is still gel-coat for a very glossy finish and good water proofing. Repairs are also easy to do, using epoxies rather than polyesters. Whether you're in the market for a new PWC, or in the repair trade, 2010 is looking a like a very interesting year. It's been a long time since so many new technologies appeared together.

iBR system in brake mode. Thrust is divided between water going forward for braking and some water going up to counteract the stern rising when in reverse.

S3 Hull has very smooth inner and outer surfaces so accurately positioning threaded nuts to hold internal hull hardware is possible. Ribs for strength can be positioned exactly where required as the closed mould process easily allows for small radius corners and fillets that are all but impossible with hand lay up.

Spray Deflectors

Steps in planning surface