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Related Resources • Maintenance Q&A Index

What causes sludge to form in oil and what can be done about it? J.L., via e-mail
Infrequent oil changes or use of improper oil are possible causes. To avoid this, change your oil at the interval suggested by your engine manufacturer, always replace the oil filter, and make sure you refill the proper grade and viscosity.

If the sludge persists, water may be getting into the lube system due to a cracked head, leaking head gasket, or cracked block. If so, call your mechanic.

What grade of sandpaper should I use between varnish coats? H.W., via e-mail
To get that really smooth finish, wet-sand with 400- or 600-grit dry silicon carbide paper and a sanding block. Make sure each coat is thoroughly dry before sanding and wiped and tacked clean before applying subsequent coats.

How long after installing a new V-belt should it be checked for tightness, and are there any other belt-maintenance tips? B.A., via e-mail
Most belts stretch after the first few hours of operation. It’s best to check the tension frequently at first. To do this, run your engine in neutral at 1200 rpm for about 15 minutes, then shut it down, check the tension, and adjust as necessary. Give it another look after about eight hours of operation, then check it again at 150 hours. The rule of thumb for tension is between one-half and three-quarters of an inch of deflection on the longest stretch when firmly depressed with your thumb. Too much tension will impose excessive load; too little causes slippage and excessive belt wear.

Preventive maintenance tips include regular inspection for nicks, cuts, abrasion, and glazing. If you find a belt that needs replacing, it’s probably a good idea to change all the belts on your engine, and keep spares onboard.

Interlux ( (908) 686-1300. www.yachtpaint.com.

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