As someone who has been on the service end of the boating world since the age of 16 one of the most often overlooked items on a boat is the propeller. Having a propeller that is not in tip-top condition can cause several problems for you and your boat. The easiest solution to a damaged propeller is replacing it with a new one however repair is usually far lest costly, and when the work is performed by a qualified shop, you can see better performance than a new propeller.
Most boaters would look at their propeller and think nothing of a small ding out of it. However, a small ding which may only be an ounce of aluminum on the outer edge of a blade that is running at wide open throttle now gets multiplied, causing an imbalance issue. Even though you do not feel a vibration one does exist. It is causing unnecessary vibrations in your outdrive or lower units gears and bearings, causing premature wear. This condition is far worse with larger props, stainless props or higher rpm units.
Large boats with brass, bronze or stainless propellers should have their props checked on a yearly basis and balanced at least on bi-yearly basis. Believe it or not even if you have not hit anything your propeller will likely be out of balance. On inboard drives or v-drives with propeller shafts, prop balance, as well as propeller shaft balance, is important. An out of balance prop can cause severe vibration, premature wear on strut bearings, v-drive or transmission bearings and shaft alignment issues. It can also cause the shaft coupler bolts to break and you could loose a shaft!
Drives with twin props, such as a Mercruiser Bravo 3 and Zeus drive or Volvo Penta DuoProp and IPS drive, should always have the props repaired and balanced in pairs. Even if only one of the two props has an issue I always recommend having both props checked and balanced.
The most important part of propeller repair is the shop that does your work. A welding shop is not a propeller repair shop unless they have all of the proper equipment. I have seen many occasions where someone had a propeller fixed at a welder and they have severe vibration or lost performance, and here is why. A propeller shop has molds for the different propellers. They also have the proper machines to balance your propeller so that there is virtually no vibration. A skilled propeller shop also has the knowledge to know how a propeller performs, the technology behind it and often how to tune it so that it will perform better for your needs. Propeller shops will also have recommendations for you if you wish to change the performance of your boat.