More of this Feature • Part 1: Ground Wire, Isinglass Care • Part 2: Diesel Exhaust, Amine Blush Removal, and more
Related Resources • Maintenance Q&A Index

I've noticed the exhaust on one of my diesel inboards is dark gray, and sometimes almost black in color. What does this mean? H.D., via e-mail
It could be as simple as a damaged or dirty air cleaner, or you may have gotten an improper grade of fuel. And while operating your engine in high ambient air temperature may also cause this, a more serious internal reason may be excessive exhaust back pressure brought about by anything from a past modification to the exhaust system to some sort of blockage. It could also be a faulty injector setting. Check the most accessible areas first before calling in your diesel mechanic.

How can I remove amine blush from a recent fiberglass job? B.W., via e-mail
Amine blush is a byproduct of the epoxy curing process and appears as a wax-like film on the surface of the area being worked on. It is usually caused by moisture from condensation or when humid conditions react with the amines in the uncured hardener material. If not properly removed it can cause adhesion problems with subsequent coatings and interfere with the curing of some paints and varnishes and all polyester gelcoats.

Do not use detergents or solvents to remove it. Amine blush is water-soluble and can be removed with an abrasive pad and water once the epoxy has fully cured. Use a 3M Scotch-brite general-purpose hand pad to abrade and dull the shiny surface. Then wipe the area with a clean, lint-free cloth and check for any other shiny spots. Once all the blush has been removed, you can continue with your project.

To help minimize amine blush, make sure to follow all manufacturers' directions. Avoid working in humid conditions or where the ambient temperature is below 65ºF, where epoxy will cure more slowly, thus allowing the blush to form. In addition, check your resin-to-hardener ratio, as too much hardener will not only increase blushing but also compromise the epoxy's strength. Finally, stir the epoxy mixture thoroughly to evenly disperse the hardener. 

I've noticed that the spark plugs on my tender's two-stroke outboard become fouled quickly. What can be wrong? M.G., via e-mail
You may be mixing the gasoline and oil at an improper ratio. Fifty parts gasoline to one part oil is the norm, but check your engine manufacturer's recommendations to be sure. Other possible causes are improper spark plugs and excessive idling.

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: kkreisler@primediasi.com. No phone calls, please.

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