Avoiding a Spun Hub

The Other day I was offshore in my fishing boat with a Yamaha outdrive. Suddenly I lost forward momentum, though the rpm picked up. Fortunately I was able to get towed back to port where the mechanic found I had a “spun hub” in my prop. How does this happen? Can I prevent it? And what can I do if it happens again?
-Darrin Smulder, Bradenton, Fla.120801-G-BI776-133 2012 Week in the Life of the Coast Guard

A prop is joined to a splined propshaft via a correspondingly splined hub and a rubber cushion. After a while, the rubber may deteriorate and shear when power is applied. Sometimes the shearing is due to repetitive strikes by the prop against harder objects. And many times it’s caused by a thermostat being stuck open, allowing only cold water to course over a rubber bushing that needs warm/hot water running over it to enable it to do its job. When you get a prop re-hubbed, directions will tell you to install the prop but let the engine idle for 15 to 20 minutes to allow the rubber to properly heat-and-seat. What to do in case it happens again? If it’s an emergency, you can come home in reverse, as the hub shears one way, and you may be lucky enough to be able to temporarily “rejoin” the shards in reverse. Keep in mind your safety, as water coming over the transom is a possibility. And keep an eye on your engine temps: too cool and you’ll continue to have problems. — GM


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