It's Good to Vent Page 2

Maintenance Q & A — July 2004
By Capt. Ken Kreisler

It’s Good to Vent
Part 2: Fuel filter plugging, and more
 More of this Feature
• Fuel starvation, and more
• Fuel filter plugging, and more
• PMY Tries... Yacht Brite Buff Magic

 Related Resources
• Maintenance Q&A Index

What is the best way to lay down a bead of caulking? V.S., via e-mail
Slowly and carefully are the two words that best describe how to approach caulking. If you push the caulking gun as you lay down the bead, cut a chisel point (two 45-degree angles) on the spout and hold the gun at a 45-degree angle. If you prefer pulling the gun, cut the spout at a 45-degree angle and hold it at a 60-degree angle as you lay down the bead. When you cut the tip for either application, make the nozzle opening slightly smaller than the bead you want.

To avoid a jagged line, squeeze and release the trigger at regular intervals and use a rag to wipe the tip as it accumulates residue.

What causes diesel fuel filter plugging? H.S., via e-mail
Diesel fuel is a complex mixture of compounds, mainly of paraffin, napthene, and aromatic hydrocarbons. Each has its own distinctive chemical and physical properties and will react differently when subjected to such factors as temperature extremes and extended storage.

One of those properties is cloud point, which is simply the temperature at which the paraffin begins to coalesce, turning the fuel cloudy or hazy. Once diesel fuel reaches cloud point, it cannot readily pass through a filter element, and the engine is therefore starved for fuel.

If you operate your engine in cold weather and are experiencing filter clogging, you can avoid this problem by using a fuel heater to maintain the fuel’s temperature above its cloud point. Check with your engine manufacturer if you are considering using one of these products, as some compatibility problems can occur.

A common cause of filter plugging is microbe buildup. Water in your fuel tank is the culprit here. These microorganisms thrive in the boundary between the water and fuel line and multiply quickly enough to overpower any fuel element. Such contamination can usually be seen as a brown, green, or black slimy coating on the filter.

Using a biocide can control the problem, but there is a caveat: With the resultant “dead bodies” piling up, this solid mass, often seen as string masses, can cause additional filter plugging. That’s why repeated changes of both primary and secondary filters is essential. To help prevent the accumulation of water in the first place, use a fuel-water separator and keep your tanks as full as possible. This will reduce the free air space in your tanks that is necessary for condensation to occur.

Need help with a maintenance problem? Write to Maintenance Q & A, Power & Motoryacht, 260 Madison Ave., 8th Fl., New York, NY 10016. Fax: (917) 256-2282. e-mail: No phone calls, please.

Next page > PMY Tries... Yacht Brite Buff Magic > Page 1, 2, 3

This article originally appeared in the June 2004 issue of Power & Motoryacht magazine.

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