| Mercury Racing Revises NXT1 Drive for Single-Engine Applications | | Print | |
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Mercury Racing revises the NXT1 drive skeg for single-engine applications. Originally published in August 2008 issue By Matt Trulio More years ago than I care to count, I took my first ride in a twin-engine performance boat with Bob Teague, this magazine's lead test driver. I was as green as a head of lettuce when it came to the performance of go-fast boats, and I made the mistake of framing a question to Teague as a statement. 
Here is what I said: "A boat with two engines must take more skill to drive than a boat with one engine." Here is what Teague said as he hammered the throttles and shook his head in disgust: "You think so, huh?" Teague cleared things up and over the years I realized that my statement could not have been more incorrect. In every regard, twin-engine boats are easier to drive than single-engine boats. That's because in a twin-engine application, the force from the rotation of one propeller is counteracted/cancelled by the force from the rotation of the other propeller. At speed or around the docks, twin-engine boats are far easier to handle than their single-engine counterparts. In a single-engine setup, there is no counter-balancing propeller to offset propeller torque and rotation. And that means that thanks to the force of propeller rotation, a single-engine boat might require as much as 10 degrees of steering input to run in a straight line. That also means that the submerged section of the boat's outdrive will be "crabbing" or running slightly sideways, and crabbing is hard on performance and handling efficiency. Taking a cue from the outboard-engine world, which sees plenty of products used on single-engine boats, Mercury Racing has come up with a single-engine solution for the NXT1 drive, which was originally designed for twin-engine applications with the HP700SCi and EU662SCi power plants. The solution is a "cambered" skeg, which effectively does the work of a counter-balancing propeller. "The cambered skeg lets you keep the gear case straight," said John Leroux, drive engineering manager for Mercury Racing. "The skeg does the work." John Scherer, the primary designer for the new single-engine NXT1 drive, added, "From the back, the skeg looks crooked, but it's supposed to look crooked. You have to start crooked to go straight." The new single-engine NXT1 drive will be offered with Mercury Racing's HP525EFI engine, the company's most popular engine offering. With the exception of the skeg, nothing about the NXT1 drive has been changed for the single-engine drive. It is in no way a "lightened-up" version of the original NXT1 drive, which has a symmetrical skeg and will still be offered in twin-engine HP700SCi and EU662SCi applications. Development of the product, which will only be offered with right-hand propeller rotation, was reportedly fueled by consumer demand. "We were getting a lot of requests for a more robust drive for the 525 in single-engine applications, particularly on the West Coast," said Rick Mackie of Mercury Racing. "We've tested it on a couple of cats and a couple of nonstepped and stepped V-bottoms, and it's always made an improvement over an NXT1 drive with a symmetrical skeg." How much of an improvement? According to Mackie, one stepped V-bottom reportedly ran 5 mph faster with the cambered-skeg NXT1 unit. "But the big thing is handling," Scherer said. "It's so much better with this drive in a single-engine boat. You don't have to hold the wheel turned to keep it running straight. It's much more balanced." By the time you read this, the first single-engine NXT1 drives with HP525EFI engines should start shipping. Price has yet to be determined. —Matt Trulio is a freelance writer for Powerboat magazine Contact Information If you like what you're reading, get more by subscribing to Powerboat magazine here. |
