What To Do If Your Outboards Not Running On All Cylinders!

Nothing can ruin a day on the water like an engine that is misfiring or flat out just running poorly!

What To Do If Your Outboards Not Running On All Cylinders? This is commonly due to the lack of one of three things. Either the cylinder isn’t getting the proper amount of air, it’s not getting fuel, or the spark plug is not firing in that cylinder.

If your engine isn’t operating properly, here are the steps that you need to take to diagnose the cylinders!

Symptoms Of An Outboard Not Running On All Cylinders

Whenever your outboard is running on all cylinders, regardless if it’s a 2, 3, 4, 6, or 8 cylinder engine. It is going to be running smoothly.

No hiccups, back fires, or issues. This is what you want to having going on with your engine.

But as with all things, for whatever reason, sometimes it doesn’t. Which is when you need to figure out what’s going on.

When the engine isn’t running on all cylinders, it’s going to be visually shaking.

Not advancing in RPM’s the way that it should, it will be sluggish, sometimes backfire.

This is referred to as a misfire sometimes, and you might also notice that it’s idling rough.

These are the main symptoms that you will find when the outboard has dropped a cylinder or two.

What Causes One Cylinder Not To Fire?

There are three main causes that will stop a cylinder from firing.

Understanding that an engine requires air, fuel, and spark in order to run. Whenever it’s not getting all or some of one or more of these.

Then that will stop the engine from running on all cylinders.

Meaning that if whatever cylinder is not getting the right amount of air into it, then it won’t allow for combustion to happen in the cylinder.

The same goes for the proper amount of fuel with that air. Without fuel, you won’t have a firing cylinder.

As well as if the spark plug or the ignition coil is not sending proper electricity to that plug to create spark.

Which is also needed for combustion.

How To Figure Out What Cylinder Is Not Firing

Now when it comes to figuring out what cylinder is not firing, this can be easier than you might think.

Depending on what type of engine you are working on of course, but in general.

You can simply unplug one of the fuel injectors or the ignition coils to each cylinder.

One at a time, with the engine running. Now you can listen to the engine and watch it.

When the engine isn’t running on all cylinders, it’s going to be shaking and sounding funny.

So when you unplug a cylinder that it is running on, the engine might shut off, but it will usually start shaking way more than it was.

And you’ll be able to see it visually. Now if the engine shuts off, plug that injector or coil back in, and then start the engine again.

Now move onto the next cylinder and unplug it, doing this one at a time until you work through all of the cylinders.

Eventually you are going to unplug one of the cylinders. And the engine isn’t going to change in sound or how it is running.

This is going to tell you which cylinder isn’t firing!

Fixing Your Outboard Cylinder Misfire

Now that you have narrowed it down to which cylinder isn’t firing, we’ll need to figure out which of the three items that we talked about earlier. Isn’t getting into that cylinder.

An easy way to diagnose the firing, is to pull the spark plug out, and swap it with another plug, depending on what it looks like.

Then repeat your test to see if the problem followed the plug, or if it didn’t. Now you can swap the ignition coil as well to test the coil.

But the easiest way is to use a spark board, or use spark plug wire pliers and leave the plug on the coil and hold it to the block of the engine. And crank the engine to see if the plug sparks.

This is a dangerous test, and we advise using the spark tester, but it is an unsafe option if you don’t have any other options, just know the risk is there to cause damage.

Now if you do have spark, you’ll need to see about the fuel issue.

You can do this by checking fuel pressure.

If you have fuel pressure, then you’ll want to pull the injector to test it.

And if it’s allowing fuel to go through it, then you are only left with the air side of things.

Now there can be more involved things and testing that might need to be taken into account.

But this will lead you and direct into the direction to getting it figured out!

Check Us Out!

If you would like some more in depth troubleshooting techniques, then you can join our Born Again Boating Academy which will teach you all about the systems that are in your boat!

You can also visit our YouTube Channel where we have other tons of testing videos to help you there, as well as some of these other articles here that can help you get your boat up and going!

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Aaron Hilligoss

Aaron has been working in the Marine Industry for over a decade and holds certifications for Yamaha and Mercury Marine. It is not uncommon for him to own and be working on at least three different boats at any given point in time!

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