How To Increase Compression On A 2 Stroke Outboard The Easy Way

So, you want to know how to increase compression on a 2-stroke outboard?

When you increase the compression ratio of your two-stroke motor, this helps to make your engine more powerful and highly efficient.

But before you start doing any compression, it is best to first test the existing compression. This way, you can achieve the best results you want without causing any damage to the engine. Keep reading to learn more.

How To Increase Compression

You need to conduct a compression test, first and foremost, to determine the engine’s viability. This way, you can also know if the engine possesses a good powerhead. The engine’s power is created as the piston moves in an upward motion in a cylinder.

Then, the fuel and air mixture compresses to a particular point, before setting this on fire. Once your mixture explodes in the cylinder, the piston gets pushed back down.

For those in the boating world, what this means is that the gears turn in the lower unit, then transforming the motion to the boat’s propeller, which causes the boat to move forward.

You may need to test the compression depending on the engine brand or type you have. Some tools are necessary to test such as a wrench and sockets, which will allow you to remove covers or plastics used to protect your ignition coils. This way, you can expose your spark plugs once the coils have been removed.

Afterwards, you need the right deep well socket, which is needed for getting your spark plugs out. Then, you need your compression tester, as well as a tool for turning your engine over. A compression tester should be widely available at your local auto shop. Some places often sell them for less than $50.

Testers include hoses with different fittings on the ends. This way, you can fit spark plug threads – no matter what yours may be. The most important thing is that the hose fits your engine. Thankfully, it is relatively standard-sized, so there should not be any problem with it at all.

Increasing Compression On A Two-Stroke Outboard

Generally, two-stroke outboard motors should have a 100 up to 120 PSI compression per cylinder. But this is just a rough estimate since you should still try to check using a compression test.

In addition, you should avoid having over 10 percent difference between your cylinders. This is very important to prevent problems along the way.

There are a number of reasons why low compression occurs. For instance, with two-stroke outboards, a leak in its head gasket is often the culprit.

Also, the piston rings may eventually fail, causing compression issues. There may also be concerns with the rod bearings located on the crankshaft as these fail.

It is easy to tell if the compression is low. For instance, power may be weaker or even lost altogether. In some cases, the loss could vary from 1000 to 2000 RPM.

If you have low compression issues, the hole shot may be damaged. The rough running when on idle may also be experienced, in addition to concerning noise in the engine while you have the motor on idle.

Other signs of low compression include mechanical issues. Basically, as long as your engine is not running well or has a rough running operation, then a low compression is often the case.

With all these things in mind, you may want to consider fixing this problem with low compression. Fortunately, it is not an impossible feat to accomplish. It all depends on when you have found the issue and how bad it is.

In other times, you can simply increase the compression to solve the problem once and for all.

Disassemble your engine then change your bearings out, as well as the rods and rings. Anything that may have failed, you simply need to remove and replace these parts. You may also want to replace the head gasket and hone the cylinders out.

When fixing a two-stroke outboard with a low compression, you would want to weigh the cost involved with this kind of task. It may be more expensive to increase the compression as compared to replacing the engine completely.

Can You Run A Motor With Low Compression?

This is an important question that many people ask, especially if they failed to increase or fix the compression level. But surprisingly, your motor can still run despite the low compression.

But then again, it also depends on how low the level is – and how severe (or not) – the problem may be. The issue is also another thing to consider since if the problem is due to other parts, then the engine may start and stop.

Low compression due to a bad bearing or carbon build-up is not that big of a problem, and the engine should still work as normal.

But do keep in mind that you will have to get this issue fixed at one point. Leaving it as it is may cause the entire engine to blow up and cause a more serious problem – a permanent issue that may be hard to address later on.

Read More: Does Bottom Paint Devalue A Boat? Important Things To Consider

Final Words

With all these things in mind, it is best to consult a specialist to help you determine if you need to increase compression on a two-stroke outboard or not. It is best to leave it up to the experts since this can be a delicate issue to deal with.

A compression test is something to consider, although if the issue is worse than what you assume it is, then a replacement of problematic parts is a necessity. We hope this post has been helpful in addressing your particular concern with the compression level in your outboard motor.

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