Magnets can help protect your engine.
By Dave Osmolski
Whether inboard or outboard, small or large, four-cycle marine engines all have one thing in common: the oil lubrication system. Although effective at lubricating the engine, the system traps particulates that enter through normal wear or an impending disaster, such as a disintegrating bearing or shaft.
In marine engines, most wear-inducing particles are metallic fines, such as iron or steel. Oil filters do a good job of trapping fines above the filter’s pore size; however, smaller particles and larger, heavier particles not drawn up through the oil pump remain in the flow.
One solution to trap and remove iron and iron-alloy particles is using a magnet-tipped oil sump plug. Many OEM plugs have magnetic tips made with alnico or neodymium magnets. Both types initially remove much of the steel fines but can lose their strength with high engine temperatures.
Standard grade neodymium magnets lose strength above 176 degrees Fahrenheit. This is OK for larger particles that sink to the bottom of the sump where the magnet is located; however, smaller particles don’t sink to the bottom, and some pass through standard oil filters. A magnet that retains its strength is more likely to remove the smaller fines passing by.
The basic argument against magnetic oil drain plugs is that those fines not removed by the oil filter remain in suspension. This may be true for automobile engines, which are used more consistently, but in marine engines, particles can sink to the bottom of the sump during periods of inactivity.
Another argument is that a properly lubricated engine shouldn’t produce metallic fines, and if your engine is producing fines, a serious problem is brewing that may require a rebuild. In either case, I would prefer to have the additional protection against particles in my oil. I would also like to know if the engine were producing more than normal amounts of magnetic fines.
If an aftermarket magnetic drain plug isn’t available for your engine, you can buy magnets to place in a row around the circumference of your oil filter. Although this method won’t warn you of excessive particle production, it will trap those particles capable of passing through your oil filter.
A ring of magnets placed around the fuel filter in diesel engines will intercept any magnetic particles contained in diesel fuel and perhaps prevent injectors from being blocked.
Aftermarket oil sump (drain) plugs are available from many sources online. I have used Dimple Products, which is owned by a friend of mine. Dimple’s magnets, found online at drainplugmagnets.com, are so powerful, I got a blood blister from a pinch between two of them!
D/Lt/C David H. Osmolski, AP, of Charlotte Power Squadron, has been repairing boats since high school when his first boat, a canvas-covered canoe with cedar ribs, leaked in gallons per minute and required constant repair.
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