Why Does My Fishing Boat Motor Smoke?

You were out fishing the other day when you noticed a smokiness in the air. You looked around, but you couldn’t be sure where the smoke was coming from. After hours of being trailed by the smoke, you realized it. Your motor is smoking! Why is this happening?

If your outboard fishing boat motor is smoking, it could be due to a cooling system clog, an overheated engine, or even a cylinder leak. It’s when you see black smoke that you should be most worried, as this smoke color is usually indicative of a serious issue.

In this article, we’ll go through and explain what it means when you see different colored smoke coming from your fishing boat. We’ll also provide troubleshooting tips along the way and discuss when you must see a mechanic to get your boat fixed. Keep reading, as there’s lots of great information to come!

White Smoke From Your Fishing Boat Motor – What Does It Mean?

Of the three colors of smoke that might emanate from your fishing boat, the least concerning is white smoke…usually. Let’s talk about where this smoke is coming from and when your hackles should be raised. 

Damaged Engine 

Outboard boat engines can convert water to vapor, and that vapor becomes smoke. This might seem like no biggie, but it’s actually a bit of a biggie. You see, the water vapor is occurring because there’s more water needed to cool down your engine.

This means your engine is overheating, which is problematic. The next time you park your fishing boat, it’s a good idea to check out your motor. 

In some instances, it could be that you were boating in the ocean and a big patch of seaweed got stuck in the motor. That caused the overheating. 

That’s the best-case scenario, as you can remove the seaweed and then be on your merry way. Yet in other cases, the motor can be on the verge of failure. It overheats if you use your fishing boat for too long.

You can try taking your engine to a professional to get it repaired, but it could be on its last legs. A marine gas engine lasts on average for only 1,500 hours, so it could be that you used yours up. You’ll have to replace it. 

Gasket Leaks 

It could even be that there’s nothing wrong with the engine. Rather, the cylinder head’s gasket might have sprung a leak. Now water enters the cylinder in excess amounts, producing a vapor that burns off as white smoke. 

This isn’t good, but at least you can rest assured that nothing is wrong with your motor. You will have to get the leak patched up and the gasket possibly replaced, but you’re looking at a much smaller bill than repairing or replacing your fishing boat motor.

Engine Warming

Going back to what we said before, not all white smoke is necessarily a cause for concern. If you turn your fishing boat motor on and it begins producing white smoke almost immediately while your engine is idling, keep an eye out.

Should the smoke die down once your boat is out and moving, then this is fine. The smoke was just part of your engine warming up. 

Is Blue Smoke From a Fishing Boat Motor Normal?

You’ve started paying attention to the color of the smoke coming from your boat, and it’s certainly not white or even light gray. Instead, the smoke is blue in color. What is this all about?

You will only see blue smoke if your outboard engine uses oil, such as a two-stroke or a four-stroke engine. These engines will burn oil with fuel, using the oil for lubrication. 

If yours is a newer two-stroke outboard engine, then it should burn fuel 75 percent cleaner compared to a standard two-stroke. That doesn’t mean you won’t see smoke at all, just at a much more reduced rate.

An increase in blue smoke in a two-cylinder engine is concerning, as it may mean that the ratio of fuel to oil is lopsided. The baseline ratio you want to achieve is 50:1, with the 1 representing how much oil should be in the mixture and the 50 is indicative of the amount of fuel. 

Switching to synthetic fuel is an option at this point, as the stuff is known to produce a lot less smoke. You can also try rectifying the oil to fuel ratio. 

What if your fishing boat is powered by a four-stroke engine? As we touched on, these motors still burn oil and thus will produce blue smoke. 

The most frequent reason that anglers report blue smoke from a four-stroke motor is due to the angle of their engine. If your outboard engine is tilted downward, then oil accumulates in the motor’s cylinders. 

When you run your boat, all that oil burns off at once, leading to a huge cloud of blue smoke that surrounds you. Try trimming your four-stroke engine at 45 degrees and see if that makes a difference.

The Dreaded Black Smoke – Determining the Source of Fishing Boat Motor Damage

As we’ve established to this point, white smoke can be normal(ish), as can blue smoke. What is never normal is seeing black smoke emanating from your fishing boat motor. Let’s address the causes of black smoke but be forewarned that none of them are good.

Incomplete Fuel Burning

Carbon can form on surfaces of your fishing boat engine when your engine doesn’t run at top speeds or when the boat idles. The injectors, rings, and valves can get coated in the stuff. 

From then on out, when you use your fishing boat motor, the fuel doesn’t burn entirely, and black smoke results.

You’ll have to remove the carbon from these parts of your boat using a product like Mercury Marine Quickleen

Quickleen is safe to use to remove carbon from the cylinder heads, piston crowns, spark plugs, intake valves, injectors, and carburetors. This fuel system and engine cleaner comes in a 12-ounce bottle. Quickleen is designed to prevent the motor pistons from seizing as well as your engine from knocking.

Stuck Fuel Injector

If you’re using your engine at full throttle and it’s still producing black smoke, then check the fuel injector. It might have gotten budged into an open position. 

In that case, then whenever you use your fishing boat, fuel is going directly into the engine’s cylinder. 

It doesn’t matter what type of fishing boat motor we’re talking about here; none are built for constantly burning fuel like that. Thus, the black smoke comes billowing out of your boat. 

When Should You Fix Your Fishing Boat Motor Yourself vs. Going to a Mechanic?

Now that you understand where the smoke is coming from and we’ve deciphered what the color can mean, it’s time to figure out what you’re going to do about your fishing boat motor problem. Here’s what we recommend. 

If the Smoke Is Blue or White, Fix It Yourself

As we’ve discussed, blue smoke is usually caused by simple issues such as using the wrong oil-to-fuel ratio or not trimming an outboard four-stroke engine. You could always see your favorite boat mechanic to give your boat some TLC, but these issues are largely fixable yourself.

If you know that the white smoke burning from your fishing boat motor is not because your engine is warming up, then you can try troubleshooting it.

Dock your fishing boat but leave it running. Does the oil temperature begin to drop? What about the oil pressure? If the latter decreases by a huge margin rather rapidly, then something is seriously wrong with your fishing boat.

We’d recommend getting it towed straight to your mechanic!

If the engine maintained oil temperature and pressure, then take your boat home and get it out of the water. You want to test for leaks. 

Park your fishing boat, connect a garden hose, run the motor, and allow it to reach its optimal temperature. As soon as that happens, use your emergency shutoff to power down the engine. 

Now remove the spark plugs. You’ll need a specialized spark plug wrench for the job. Take the starboard’s top cylinder and feed a compression gauge through it. 

Then crank your engine, doing this three times. Track the rate of compression for each crank, then void your compression gauge. Keep testing each cylinder and then put the spark plugs where they came from.

Next, run your fishing boat engine again until it’s warmed up. Then take some water and shed the droplets on the exhaust riser. Does the water immediately evaporate? That’s indicative of an issue with the exhaust manifold. You’d have to see your mechanic at that point.  

If the Smoke Is Black, Go to a Mechanic

Black smoke is usually quite a big issue, so we wouldn’t recommend tinkering with your fishing boat. Wrap up your day of fishing early, tow your boat, and go straight to your mechanic’s if you can. 

If You Can Pinpoint the Issue, Fix It Yourself

Perhaps using the troubleshooting tips from above or your own methods, you were able to figure out what’s wrong with your boat. Knowing is half the battle, that’s for sure.

If you’re confident in your abilities to fix the issue, then there should be no need to get a boat mechanic involved.

That said, you want to monitor the issue over the next few weeks to see if the matter recurs. If it does, then your mechanic should probably check out your boat. 

If You Have No Idea What’s Wrong with Your Fishing Boat, Go to a Mechanic

Listen, it’s okay to admit you’re clueless about what’s happening to your fishing boat. Rather than waste time scratching your head and potentially worsening the issue by continuing to use your boat, call up your mechanic and see when you can bring your boat in. 

Final Thoughts 

Fishing boat motors can produce smoke in white, blue, or black. The color usually indicates the severity of the issue, but not always. Black smoke can be a very severe issue whereas sometimes blue smoke isn’t.

All smoke from your fishing boat isn’t bad, but if the smoke is billowing or comes out in large quantities, you need to get your boat checked out, stat. 

Tim Butala

My name is Tim and I have been a fisherman my whole life. My favorite fish to go after is a Striped Bass.

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