What exactly is a N2 Violation? - NBC Right Now/KNDO/KNDU Tri-Cities, Yakima, WA |

What exactly is a N2 Violation?

Posted: Updated:

We all know that the title of "Unlimited Hydroplanes" is a bit of a misnomer.  In fact, the boats are limited in both fuel flow and N2/RPMs.  Drivers have to consistently monitor the situation to make sure they stay within the proscribed limits to avoid being penalized.

Hydroplanes have an on-board warning system to let them know when they're close so they can back off.  Sometimes it's as simple as a light that flashes when they exceed the limits and they manually count off the time and back off the gas for a second to bring them in compliance and then mash it again.

Here are the official rules from the ABRA rule book:


A fuel flow violation is judged to have occurred when a turbine-powered boat exceeds 4.3 GPM for more than five seconds. The boat then forfeits all points earned for that heat. Any boat found to have a fuel flow violation during the Final Heat is disqualified.


An N2 speed violation is judged to have occurred when the maximum N2 RPM of 110% is exceeded for more than five seconds. Any turbine-powered boat found to have an N2 speed violation shall forfeit all points earned for that heat.  Any boat found to have an N2 violation during the Final Heat is disqualified.

Violating these rules in qualifying will also negate any official times posted during that run.

Steve David, drive of the U-6 Oh Boy! Oberto/Miss Madison explains that the fuel controls for the Lycoming engines in hydroplanes are extremely sensitive.

"Generally, after a test session or two every team has their fuel pretty well dialed in," he wrote on the Hydropage Forum.  "The freak incidence usually happens where a team is coming up for a start and hammers it. The immediate pressure rush sends the fuel flow to the moon and sometimes doesn't drop back to 4.3 unless the driver backs off for a split second. As long as the driver catches that before 3 seconds has lapsed, you're fine from a tech inspection standpoint."

David goes on to say that every fuel control seems to have it's own personality and takes some getting use to. "Most of us have gauges in the cockpit, or lights, for overspeed above 110 N2 and fuel flow over 4.3 Sometimes in qualifying you'll be right on the edge and literally counting or stop "watching" to back off, reset the governor (which is mechanical) and get back on it, all within 1/10th of a second or less."

"If you're at one of our races, listen carefully during qualifying and you may hear a boat or two doing just that," David said.  "In the actual racing the fuel flow can be a problem as mentioned, normally N2 falls a few points in the rougher water. You might qualify at N2=(essentially prop speed) 109-110 and in race conditions see 107-108."

Fastest qualifying times wiped out by N2 violations >>

One boat Friday and four boats Saturday lost their qualifying times due to N2 violations.