What’s Your Next Prop?

If your repowering project involves switching to bigger engines, a shop with state-of-the-art computer programs can predict what kind of improvement you’ll see in performance, whether you’ll need new props (chances are you will), what specs they should have, and what they’ll cost. Knowing what you’ll get versus what you’ll pay will help you decide whether to repower with the same engines, or go for more horsepower.

The shop can also analyze your current props by physically measuring them with sophisticated hardware, making sure all the blades are pitched equally, have the same blade-tip distances, and the pitch and diameter are what you think they are. Sometimes just tuning the props can make a noticeable difference in performance. As boats get older, they tend to get heavier; maybe your engine doesn’t have the oomph it did when it was young, so your original props may not be correct today.

Before contacting the shop, gather as much performance info about your boat and engines as you can: not just speed versus rpm, but operating and exhaust temperatures, running angles, fuel burn, engine hours, reduction gear, and so forth. The more information you provide, the better the info the shop will produce.

To find a high-tech prop shop in your area, check the Hale MRI ( halepropeller.com) and Prop Scan ( props. com.au) websites. Shops using high-tech prop analysis can do a really good job of bringing your propellers up to spec, or selling you new props to match your new engines. They are worth their weight in Nibral.