Time to Replace the Propeller

How do you know when it’s time to replace your boat prop? I mean, sometimes it’s obvious, like when you hit a rock and it shreds the propeller blades. However, the gentle scrapes and bumps throughout the boating season leave minor marks, but is it enough to warrant a new prop?

Damage to the propeller blades can cause multiple problems.

The truth is that propellers are a precisely engineered and machined part on your boat. It’s where the rubber hits the road… but on the water. Prop damaged, no matter how slight, will reduce performance, consume more fuel and lower your top speed. With gas prices being what they are, that’s something that no boater wants. Replacing a dinged prop will reduce drag and help the motor’s efficiency.

However, this isn’t the worst part. Any ding or bend on propeller blades will throw the prop out of balance. This can sometimes be felt with excessive vibration. An unbalanced prop puts a lot of wear and tear on the lower unit, especially the carrier bearing and seal. If you don’t take care of the seal and it leaks, the lower unit can be damaged permanently.

Lower units are expensive, and breaking down on the water can be outright dangerous. When a boat motor breaks down you can’t simply walk for help. Depending on where you are boating, a break down could involve flagging down a fellow boater for help or much more serious safety issues. And let’s not forget the bill if a tow is necessary… tow boats charge from when they leave their dock until you get dropped off.

By inspecting your prop regularly, you can save in the long run. All damage to your propeller decreases efficiency and can result in engine damage. iboats.com has a complete selection of replacement aluminum and stainless steel propellers.

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3 Responses to Time to Replace the Propeller

  1. Tom Clark says:

    You can always tell when it is getting near to a prop change, as the vibrations pick up and normally get worse over the subsequent weeks.

    Great article Toby



  2. Clyde Zellers says:

    Can anyone comment on loss of propulsion scenarios? Cruising along, didn’t hit anything, that I could tell, engine revved up and then no go. Is it one of three possibilities?
    1. Spun Prop
    2. Lower Unit.
    3. Engine Coupler.
    Question; how do you tell what one of these it may be?
    I know pulling the prop should lead to a quick answer but how do you tell the difference between an Engine Coupler and a Lower Unit problem? What goes wrong with the lower unit that would make it malfunction?
    Thanks, Clyde

  3. Chris Horvath says:

    I had a similar scenario, twice, with an early 80′s OMC out drive. In my case the intermediate drive shaft was a two piece unit welded together at the factory utilizing a “spin weld”. The weld broke resulting in exactly the situation you describe. Luckily it was covered under warranty both times and I sold the boat before it had the chance to do it again. Hopefully this isn’t the case in your situation, but it does sound more like lower unit than prop related?

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