What would break a boat's propeller while out at sea?

Question

In deep water, without there being any rocks to hit, what would cause part of a steel prop to break off?

Answer 1

There are all kinds of things floating around out there. I've done a number of repairs on boats that hit mystery stuff.

Answer 2

The ocean is full of debris. Striking a partially submerged log, an old boat hull, even a whale or a large fish can fracture a prop blade. Also, metal fatigue and wear, a process called "electrollosis" which is a corrosive electrical current that is caused by metal on a boat reacting with salt water can wear out  a prop blade if you do not have the correct "zinc" ball or other set up to controll it. In short, there are lots of things that can cause it.

Answer 3

The other answers are very good.  I would also suggest you use a stainless steel prop as aluminum is adversely affected by salt water.  Objects that are semi buoyant will float just below the surface of the water, and cannot be seen from above the water are a real danger in both fresh and salt water.  In my experience with having to repair and replace many aluminum props, I have found that a stainless steel prop will survive more than an aluminum prop.  The skeg on the bottom of the lower unit is intended to help protect the prop as well as help act as a rudder when turning the motor.  Make sure the skeg in not damaged or worn down.  They can be repaired.  Many props are damaged when pulling away from a cement launching ramp.

Answer 4

Jaws

Answer 5

Broken drive shaft

floating debris

discarded fishing nets

large sea creatures

anchor tangle

anomolies such as poor welds on props

hairline cracks in prop

broken bearing and bushings on the hull

Answer 6

logs

Answer 7

metal fatigue...hairline cracks...unseen debris...plenty can cause this.

Answer 8

no mateniece, poor casting ,hairline cracks,sandbars, bad things floting in the water

Answer 9

severe imbalance in an older prop anything over 18in prop

Answer 10

fatigue of the metal, corrosion, poor casting of the material during manufacture, severe imbalance of blade loading.

Answer 11

lobster pots!

fatigue in the metal

lack of general maintenance