Clanging noise is seldom a good thing

George Seacrist learned to hunt squirrels years ago from his dachsund. Now he’s extremely successful at the sport.

When I opened my e-mail recently, I found this note from a boater in Kentucky: “Hank, I found you on the web and hoping you can help. I was on Lake Cumberland in Kentucky yesterday, and had to be towed in. I have a 1998 V-6 outboard. I was running about 3 miles at wide open throttle, approximately 50 mph, and heard a loud clanging sound out of the engine. I immediately shut down the engine, and as I turned to look, saw a puff of smoke come out of the cowling. I sat for a minute then tried to turn her over, and it was locked up tight. I waited about 30 minutes and tried again, and although she turned over, the clanging noise was evident. I didn’t want to do any further damage so I got towed in. Any thoughts or ideas would be greatly appreciated.”Unfortunately, loud clanging noises coming out of your engine are very rarely a good sign. In most instances, it is an indication of a major failure either in the power head or lower unit. The power head could have a damaged piston or broken connecting rod, and the lower unit could have broken gear teeth. What you should do at this time is run a series of checks on your engine to determine where the problem is located.

Any time you are going to work on your engine, the very first thing to do is a compression test. This will tell you the condition of the inside of the power head.

You can purchase a compression gauge at most tool suppliers. Screw the gauge into each cylinder, and have someone spin the starter for you. Monitor the gauge, and continue spinning the starter until the indicator needle no longer climbs up the scale. Write down this reading for each cylinder.

Different engine brands have different compression readings, so it will be necessary to refer to your service manual for the recommended reading for your engine. The cylinders will not always be exactly uniform, but there should be no more than 10-percent variation from the highest to the lowest reading.

If your loud clanging noise was the result of a piston or rod failure, then when you check compression on the failed cylinder, that reading will be excessively low, possibly even no reading at all.

If all six of your cylinders have good compression readings, you can look elsewhere for your problem. The next most likely spot for that noise would be the lower unit.

Before attempting to disassemble your lower unit, try sampling the oil in the unit. When gears or bearings tear up, they create a large amount of metal shavings in the lower-unit oil. Many motors today have magnets attached to the drain plug of the unit. Remove the drain screw, and check for metal pieces stuck to the magnet. If you find this, the lower unit should be disassembled and inspected for damage.

Some engines do not have the magnetic drain screw. If this is the case with your engine, then drain a small amount of the oil onto a shop towel. Fold the towel over and blot the excess oil. If you have a gear or bearing failure, you will see metal particles on your shop rag when you open it up.

If you are not certain what is causing the noise, remove the lower unit from the engine. With the lower unit off, crank the engine and note if the noise still exists. If it is still there, the problem is in the power head. If the noise is no longer there, you can look into the lower unit.

Power head and lower unit disassembly and repair is a lot more technical than your average tune-up or water-pump job. You may want to consult with your local marine dealer and possibly have him disassemble and estimate your repairs for you.

Keep in mind that your engine is a 1998 model. Before proceeding with major repair work, be sure to get an itemized estimate and compare that to the blue book value of your engine. Although it may cost less than a new engine, it could be a mistake to spend more on repairs than the engine is actually worth. Before exceeding the blue book value of the engine, consider the fact that no matter how much you spend on this engine, you will still have a 1998 model engine and the value will not be increased. Also realize that no matter what parts are changed, you will still have an enormous amount of other 1998 model parts that can and will break some day. What happens if some of those parts become another major repair?

There is also one other thing to consider. What if something completely beyond your control happens to the engine? For example, you are heading to the lake one day and you are involved in an accident. The other driver is at fault so you figure his insurance company will make good the repairs or replacement of your engine. Wrong! The insurance company may only cover up to the blue book value of the engine. You protest that you just spent all that extra money having your engine repaired. They say they are only responsible for the book value. Here is your check. Have a nice day.


In the November issue of Louisiana Sportsman, I wrote about insects, such as mud-diver wasps, that build nests inside engine covers and can cause severe damage to your engine. I received this e-mail from Wayne in Mississippi: “Just read your article in Louisiana Sportsman about dirt divers building under engine covers. I’ve had six bass boats in the last 30 years, and that happened to me once. Since then, I have taken the cowling off and put three or four moth balls on each side of the motor in the bottom of the cowling. I also put them in boat compartments. They work like a champ. No critters. Just thought you may want to try it.”

Thanks Wayne, you may have just saved several engines.

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