Marine Muscle
How Much Horsepower Do I Need?
When it’s time for a new outboard, bigger isn’t necessarily better; you have to match the outboard to the way you use your boat, your budget, the size and type of boat; and the vessel’s weight and horsepower capacities.
Horsepower Ratings – Not Quite 20’
Due to their smaller size (length, beam, bottom width, transom dimensions, inside hull depth), boats less than 20’ length overall (LOA) don’t have as much inherent buoyancy and stability as their larger kin; therefore these craft must comply with government-mandated methods to determine a reasonable engine size.
The U.S. Coast Guard has definitive formulas and tests to establish the Maximum Persons Capacity (in pounds) and the number of people; the Maximum Weight Capacity (persons, outboard, and gear), and Maximum Horsepower that an outboard-powered boat under 20’ can safely handle.
This information is readily accessible on the U.S. Coast Guard Maximum Capacities label in the boat.
Outboards for Under 20-Footers
Boats 16-20’ are one of the best-selling product segments in the marine industry, because if you do your shopping, they’re reasonably inexpensive, easily trailerable by a mid-size tow vehicle, and one person can usually launch, operate and retrieve the boat alone.
It is important to make a determination for yourself about how an engine’s power relates to a boat it is matched with. Make sure you test drive the boat to see if the price-point outboard will suit your needs.
For example, a typical 17’ aluminum fishing package can have a Maximum Capacity of 90 hp, but you can buy the boat with a 25, 40, 50, 60, 70, 75, or 90 hp outboard, emphasizing the fact that on a smaller craft (shorter than 20’), engine choice is frequently a juggling act between initial cash out of pocket and your long-term satisfaction with the boat.
HP Ratings: Boats 20’ and Longer
Because the official (weight capacity and horsepower) calculation rules pretty much exclude boats over 20’ LOA, we went to Joe Hunter, Engineering Manager of Grady-White® Boats to get the inside scoop on how manufacturers go about rating their larger (greater than 20’) vessels.
Hunter said, “We start by partnering with a naval architectural firm that calculates the required structure for the horsepower needed to obtain the desired performance. In addition, we have built many models in this size range over the past 40 years and have a large amount of empirical data for comparison.
Finally, we conduct extensive testing and sea trials on the finished product with the maximum horsepower to insure optimum performance and safe operation under a variety of conditions.  |