how to tell if oil injection is working on outboard

Checking the oil injection system regularly is a great way to ensure that you run well on your next excursion. But how to tell if oil injection is working on outboards?

Today, we will share four tests to apply to this system. Each requires a specific set of tools and gives different signs. Let’s see how they can help you! 

How To Tell If Oil Injection Is Working On Outboard? 

We recommend four tests for checking the functionality of your jet ski’s oil injection system. No matter which method you choose, remember to check the boat’s manual first.  

Manual test

Manual testing is the most effective method for checking if the oil injection system is still functional.

For safety purposes, you must spray little oil on the carbs. Even when the oil pump is malfunctioning, this tiny amount of oil guarantees the motor has some lubrication.

Find the oil pump valve, then pull it up. Next, start the engine and let it stand for roughly 30 seconds. You may need to add some oil for the carbs using this technique.

The extra oil will produce a lot of smoke if you add some throttle. You can be confident that the oil injection pump on your jet ski still works if it emits smoke like a chimney.

Pressure test

Another method to test the oil injection system is a pressure test. This method works well if you have replaced or detached its components. 

If you choose this technique, please note that it can differ from model to model. Hence, check your boat’s manual carefully before carrying out the test. 

Prepare a leak tester tool for this method. The kit has a small pump and a gauge that you can attach to the vent line of the fuel reservoir. 

Start by filling the fuel reservoir and installing hoses on the oil lines. You may perform these tasks frequently. 

Next, pressurize the injection system to a certain degree. If you can’t maintain the pressure, check the connections and hoses for leaks. 

Remember that even when you have sealed the system completely, it doesn’t mean that the oil pump can still work correctly. 

Drill test

You can also remove the oil pump from the system to check if it’s in good condition. This test sounds straightforward, but it will leave a mess.

So please follow these steps:

  • Detach the fuel lines and remove the pump from the motor with a drill.
  • Place the pump in a vise, and then firmly tighten it.
  • Connect a rubber hose to the input nipple. Then, fill it with engine oil. 
  • Release the bleeder screw because the pump won’t work if the air prevents it from functioning. 
  • Put the pump shaft on an electric drill and whirl it gently.
  • If the pump is operating properly, you should notice oil leaking from the output nipples.

Visual test 

If the oil injection sites in the intake manifolds are accessible, you can thoroughly check the engine visually. Here is how to do it: 

  • First, reapply grease to the chambers or fuel injection to ensure that the engine has some lubrication.
  • Disconnect the spark plugs, turn off the oil line, and then crank the motor while keeping the throttle wide open. The engine may run much more quickly because there are no spark plugs.
  • If the oil pump works, engine oil should leak from the manifolds.
how to tell if oil injection is working on outboard

2-Stroke vs. 4-Stroke Outboard Motors 

Testing is not the only thing to discover about the oil injection system. The boat motor plays a vital role in this system’s functionality. 

There are two types of outboard motors: 2-stroke and 4-stroke. Which can help the oil injection process better? Let’s check. 


Reliability is one of the most important considerations when selecting an outboard motor. You want to pick a secure, reliable, and worry-free unit.

Thankfully, the 2- and 4-stroke engines currently available are highly reliable. They can power any journey and can last long. 

Whenever in doubt, conduct online research and review the reliability rankings of various motors.

Speaking with boaters with first-hand experience with various boat and motor designs can also be beneficial.


Choose the engine weight based on your boat’s weight. For example, smaller boats can’t bear heavy components. Hence, do not select a hefty engine for it.  

People who are concerned about the motor’s weight often pick 2-strokes because they are more lightweight.

On the other hand, although the 4-stroke engine is lighter than it used to be, it’s not the ideal option for your small boat. 


A 2-stroke engine used to be a popular choice among speed lovers.

Nevertheless, 4-stroke outboard engines have improved in weight and speed, which has increased competition. 

The difference in speed of motors isn’t always about whether you choose a 2- or 4-stroke model.

Every manufacturer is unique, and products from the same maker can differ among themselves. So, the best way is to conduct your research and make a comparison. 

Fuel economy

2-stroke engines consumed more fuel. The 2-cycle item’s mechanisms for injecting fuel into the engine are now significantly more efficient. 

how to tell if oil injection is working on outboard

Frequently Asked Questions 

1. How do you check an oil injection?

You can perform one of these four tests to check the system: manual, visual, drill, and pressure. 

2. How does oil injection work on an outboard motor?

Oil injection’s primary goal is to make things as easy as possible for the user. 

Some people have difficulty mixing oil and gasoline before pouring the mixture into the tank. Yet, the oil injection system automatically measures your oil level. 

3. Is premix better than oil injection?

Premixing the engine’s gasoline and oil may seem laborious, but if you have the correct tools, you may have total control over the oil mixture.

On the other hand, the oil injection system can meter oil automatically. Yet, there is no precise way to know how much oil to add. 

So, it’s up to your preference to determine the better one. 

4. Can you mix injection oil? 

Yes. Since engine oils have similar ingredients, they are generally compatible with mixing.  

Read More: Outboard Not Running On All Cylinders: Symptoms, Causes & Solutions


There are four tests to tell if the oil injection system in your boat can work properly. Follow our guides and take immediate action if you detect any errors. 

Some people are not confident about their mechanical skills. If you feel the same, we recommend sending your system to a professional. 

Hopefully, you have found what you need from our post. For any further information, please feel free to ask. Thank you for reading! 

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