Q: Should I use an aluminum or stainless steel prop? What’s the difference?
A: The primary reason to use stainless steel is durability–a stainless steel propeller will last a lot longer and will not be damaged by minor impacts that could tear up an aluminum prop. There are also performance advantages, because stainless props are typically more sophisticated than aluminum props–manufacturers will invest more in their design. So with a stainless steel prop, expect better all around performance–hole shot, speed, ability to stay on plane, better gas mileage. The downside? The cost to buy and repair stainless steel propellers can be double aluminum. And if you hit something very hard you can do more damage to the drive train–stainless steel won’t give like aluminum.
Q: What’s the difference between a 3 blade and 4 blade outboard or stern drive propeller?
A: More blades will give you better efficiency, hole shot and stern lift, but usually not as much top speed due to the drag created by the extra blade On a typical outboard or stern drive, we find that a 3 blade prop provides the best overall performance. If you do a lot of watersports, or fish in shallow water, you might want a 4 blade for the hole shot. Also, the new 4 stroke outboards create so much weight in the stern that a 4 blade is a must to lift the tail end and reduce squatting. So a 4 blade is typically best for special applications.
Q: How many blades should there be on the propeller on my straight inboard boat?
A: There are a lot more design considerations when propping out an inboard. Typically on small and light boats 3 blade props will be fastest and most efficient. But most inboards will benefit from extra efficiency created by a 4 blade prop. On smaller ski boats, the extra blade gives better hole shot and keeps the boat on plane at lower speeds for wakeboarding. On bigger cruisers, the 4th blade can create more efficiency at cruise and a smoother ride. On bigger, faster cruisers you’ll often see 5, 6, 7 or even 8 blades–you need all that blade surface to harness all the horsepower those big boats create.
Q: Is my prop repairable?
A: Most times, it is. Very few propellers can’t be brought back to “like new” condition. Some exceptions include missing blades (up to about 1/3 gone is usually worth fixing) and severe electrolysis–those props won’t weld.