Bearing Failure

Maintenance Q & A — March 2005
By Capt. Ken Kreisler

Bearing Failure
Causes for cutlass-bearing wear, starter troubles, and more.
 More of this Feature
• Bearing Failure, and more
• Keeping fuel out of the bilge, and more
• PMY Tries... Drilltec’s Sea Basket

 Related Resources
• Maintenance Q&A Index

What are the causes of cutlass bearing wear and failure? J.A., via e-mail
Premature failure of a cutlass bearing can result from operating in unusually shallow water with a sandy bottom, a condition in which silt, rocks, and shells work their way into the bearing and rapidly abrade critical surfaces. Also inadequate cooling, perhaps caused by the wrapping of a foreign substance such as a weed, a plastic bag, or monofilament around the shaft, can restrict normal water flow. Other possibilities include a misaligned drive train as well as a bent and/or scored propeller shaft.

Cutlass-bearing wear is typically related to prop-shaft speed; the faster the shaft, the faster the wear. On boats with slow-turning propellers, cutlass-bearing life can range to four years and/or 1,000 hours. Regardless of the kind of boat you have, however, your cutlass bearing will eventually wear out, so regular inspection should be part of your maintenance regimen. If you’re constantly tightening the prop-shaft nut to reduce water flow, your bearing is probably at the end of its life. If you let a worn bearing go too long and the shaft has already been scored, you’re looking at perhaps replacing the shaft as well, a considerable added expense.

My starter turns but will not start my gasoline-powered inboard. Before I call in a mechanic, is there anything I can do? R.V., via e-mail
Begin by checking the status of your starter battery. A partially discharged battery could have enough power to turn the starter but not enough voltage to fire the spark plugs. If this is the case, use a fully charged battery to get things going and charge the battery in question. If it doesn’t hold a charge, you need a new one.

Defective or corroded wiring may also be at fault. Make sure all battery-cable ends are free of corrosion, all connections are secure, and all insulation is intact. In addition, make sure the wir-ing is of the proper gauge to handle the load.

If after all this it’s still a no-go, you most likely have a bad starter motor that is drawing too many amps. Either remove the motor yourself and take it in to be bench-checked or let your mechanic handle the job.

Next page > Part 2: Keeping fuel out of the bilge, and more > Page 1, 2, 3

This article originally appeared in the February 2005 issue of Power & Motoryacht magazine.

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