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How Does Oil Injection Work on a Jet Ski? [Explained]

How Does Oil Injection Work on a Jet Ski? [Explained]

How does oil injection work on a jet ski?

Oil-injected 2-stroke jet skis have an 0.8-1.5-gallon oil reservoir to store the 2-cycle oil. The heart of the system is its oil pump, which is mounted between the reservoir and the engine. This pump is controlled by the throttle lever in most jet skis; the more throttle you apply, the more oil the pump delivers to the intake manifold, where it mixes with the gas.

If you want to find out more about this system, you’ve come to the right place. We at JetDrift have compiled all you need to know under one roof!

You might also like:Oil Injection vs. Premix: Which is For You?How do You Bypass the Oil Pump on a Jet Ski? How to Replace Ruel Lines on a Jet Ski How to Test the Oil Pump on a Jet Ski

The Origins of Fuel-Injected Jet Skis

Unlike their modern 4-stroke counterparts, vintage 2-stroke jet skis burned the oil with the gas. Due to their technology, the engines of these machines got their lubrication from the fuel.

But how did the oil get into the gasoline?

The old-school way was by mixing the oil with the gasoline in a separate fuel can, which was a big hassle.

To make life easier for riders, jet ski manufacturers developed an innovative oil-injection system.

The first oil-injected 2-stroke jet skis appeared in the late ‘80s.

Although the first vintage Yamaha WaveRunners like the 1986 WR500 and the WaveJammer ran on premix, the manufacturer switched to oil injection shortly thereafter.

In contrast, the first oil-injected Sea-Doo was the 1988 SP featuring a 580cc, oil-injected twin engine.

How Does Oil Injection Work on a Jet Ski?

The oil-injection system on a jet ski consists of five main parts, which are as follows:

  1. Reservoir
  2. Oil pump
  3. Pump cable
  4. Oil lines
  5. Gauges/Warning light
Let’s get down to the nitty-gritty and talk about each in detail!

1. Jet Ski Oil Reservoir

As a rule of thumb, each oil-injected jet ski has a separate oil reservoir mounted somewhere inside the hull.

These plastic fuel tanks usually have a capacity of 0.8-1.5 gallons depending on the make and model.

It’s a lesser-known fact that this tank can serve multiple purposes on certain models. For example, on Sea-Doos, 2-stroke oil is used for engine lubrication and to lubricate the rotary valve shaft drive gear.

As you do with fuel tanks, it is wise to also top off the oil tank on a jet ski before each ride.

For safety reasons, it’s also a good idea to carry an extra bottle of 2-stroke oil on the jet ski in secure packaging. You never know when you will need it!

Early vintage 2-stroke skis ran on premix, so they came without an oil reservoir.

2. Jet Ski Oil Pump

The heart of a jet ski’s oil-injection system is arguably the oil pump, driven by the engine with gears.

This pump is designed to move the oil from the reservoir into the engine. Oil is delivered to both the intake manifold, where gas mixes with oil and air, and finally this mixture enters the cylinders.

Are you wondering where the oil pump in a jet ski is?

The general rule is that this tiny mechanical pump is installed in the oil line between the engine and the oil reservoir. It’s typically mounted on the stator flywheel (magneto housing) cover.

On most Sea-Doos, you can find the pump below the carburetors and the intake manifold, while on Yamaha WaveRunners, the pump is attached to the front of the engine.

(If you can’t find the oil pump in your jet ski, just follow the oil lines from the reservoir or the engine.)

3. Jet Ski Oil Pump Cable

It’s safe to say that the oil pump is throttle-controlled on most jet skis, meaning that it’s connected to the throttle lever with a cable.

On a 2-stroke oil-injected jet ski, when you pull the throttle lever, you simultaneously pull the throttle cable and the oil pump cable. The more throttle you apply, the more oil the pump delivers to the engine.

It’s as simple as that!

This cable is attached to a little arm on the pump, which pulls against spring tension. When you pull the throttle trigger, the cable moves this arm, and the pump feeds more oil.

When you release the trigger, the spring pulls the arm back, which causes a decrease in oil pressure.

Are you wondering what happens if the oil cable brakes on a jet ski? Will it leave the engine without lubrication?

The good news is that the answer is no!

Keeping safety in mind, the spring moves the arm beyond the closed position if the cable breaks. This position keeps the pump wide open to deliver maximum oil, which can prevent an engine seizure.

However, it has to be mentioned that the first jet skis utilized static oil pumps, which delivered the same amount of oil regardless of the engine’s RPM.

These models were prone to smoking a lot and fouling the spark plugs when idling. This is because the engine requires less oil at idle and more at open throttle.

If a jet ski’s oil pump doesn’t have any linkage to the throttle, it’s a clue that it’s a static pump.

4. Jet Ski Oil Lines

The pump is connected to the engine and oil reservoir with rubber hoses, also known as oil lines.

Unfortunately, these hoses are prone to aging or falling off, resulting in a seized engine.

Contrary to popular belief, jet ski oil pumps are quite reliable. When a jet ski’s oil-injection system fails, in most cases it is not caused by an oil pump failure!

Instead, the cause is the rubber hoses. Over time, hoses become dry and cracked or they just fall off due to improper fastening.

Because of this, the oil lines on a jet ski require regular inspections and periodic replacement.

You can also find a small oil filter in the system, mounted between the pump and the oil reservoir on many skis.

On Sea-Doos, you can typically find a second oil line coming from the reservoir to the engine. This line is intended to lubricate the rotary valve drive gears.

5. Gauges

Jet skis typically feature an oil level gauge or a Low Oil warning light that tells you when the tank’s oil level drops too low.

The latter is often a red indicator light with an oil symbol in the fuel gauge or a feature built into the LCD dashboard. But it is always best to refill the oil tank before this warning appears.

This is because there’s no “emergency stop” built into a jet ski oil injection system if you run out of oil.

With an empty reservoir, the pump will run dry, which results in an instant engine seizure.

Takeaway – Related Questions

As a takeaway, we’ve answered the most common questions about 2-stroke oil-injected jet skis!

What is an Oil-Injected 2-Stroke Jet Ski?

Oil-injected 2-stroke jet skis utilize an oil-injection system designed to mix 2-stroke oil into the gas. Oil-injected jet skis became more prevalent in the early ‘90s while earlier models ran on premix.

How Does an Oil-Injected 2-Stroke Jet Ski Engine Work?

Oil-injected 2-stroke engines came with an advanced oil-injection system featuring an oil reservoir, an oil pump, a cable, as well as fuel lines. The 2-stroke oil is delivered into the engine from the reservoir to the engine by a mechanical oil pump. This gear-driven oil pump forces oil into the intake manifold, where the gas mixes with the oil. Eventually, this mixture is sucked into the cylinders.

On 2-stroke oil-injected Sea-Doos, this oil lubricates the rotary valve shaft gear; this is why you can find a second oil line coming from a Sea-Doo oil reservoir.

Does Oil Injected Mean It’s a 2-Stroke Jet Ski?

Yes, if a vintage jet ski is labeled “oil-injected,” it’s more than likely a 2-stroke oil-injected model.

What Year Did Sea-Doo Start Oil-Injection?

The first oil-injected Sea-Doo was the 1988 Sea-Doo SP, which is also considered the first “modern” Sea-Doo in history.

What Year did Yamaha WaveRunners Start Oil-Injection?

The first oil-injected Yamaha PWC was the Yamaha WaveRunner VXR650 (Marine Jet 650TX), released in 1992.

Do Jet Skis Have Crankcase Oil?

Yes, but only 4-stroke jet skis have crankcase oil.

Does a 2-Stroke Jet Ski Have Crankcase Oil?

No, 2-stroke jet skis don’t have any crankcase oil since these machines get their lubrication from the fuel.