Grass Roots Drag Racing

The Upper Midwest Power Boat Association Keeps It Simple

Drag racing may be the most elemental of motorsports – a short, furious sprint from start to finish line, first one there is the winner. The goal of the Wisconsin-based Upper Midwest Power Boat Association (UMPBA) is to keep powerboat drag racing as uncomplicated, and as much fun, as possible.

Brett Suebert, president of UMPBA, in his STV

“The goal of UMPBA is to have as few rules as possible,” said UMPBA President Brett Seubert. “We want to grow this sport by getting more competitors and fans engaged. Our rules make the sport easy to understand and leave a lot of room for creativity.”

The UMPBA hosts a form of bracket racing, but instead of the brackets being organized by elapsed time (ET), drivers chose to enter a bracket based on boat speed at the end of an 800-foot course. If they exceed that speed, they automatically lose. The seven brackets start at 65 mph, and go up in 10-mph increments to the Unlimited bracket, for boats able to top 116 mph. Like any drag race, success is based more on quickness than top speed. A boat able to out-accelerate a faster competitor – or the driver with quicker reaction time at the start – may end up winning the race. Boat speed is monitored by a GPS unit that’s required to be in every boat, which can be inspected at the end of each run.

Boats and competitors are required to meet basic safety standards. Racing is open to boats powered by outboards, inboards and jet drives. Each event has 35 to 45 entries, according to Seubert, with 45 to 55 class entries as some boats enter more than one speed bracket. This is real “run what ya brung” racing, and in the slower classes it’s not uncommon for fast family runabouts and bass boats to enter.

Nick Petersen, Mercury Racing Propeller Specialist

“I have four seats in my Hydrostream Venom, and I use it as a day cruiser between races,” said Nick Petersen, Mercury Racing Propeller Specialist and Project Manager, who competes at UMPBA events. “My boat is powered by a Mercury Racing 250 XS, and I started in the 75 mph class, and have moved up to the 85 mph class. Once you get up to the 95 mph class, most of the competitors are running dedicated race boats with two-stroke racing outboards that can pull a lot of RPM. A Mercury Racing 2.5 outboard can run up to 9000 RPM, so they can rig a smaller-pitch prop for hole shot and still make top speed at the end of the run.”

The faster classes are dominated by lightweight 18- to 20-foot hulls produced by brands like Checkmate, Allison, STV and Hydrostream; with pad-bottom V-hulls and Mod-VP style tunnel hulls.

“Weight is the real key to quick acceleration,” explained Petersen, “and some of the really fast hulls weigh only about 400 pounds. They’ll have a very thin carbon fiber layup, a small fuel tank, and a single center-mounted seat. Add a lightweight outboard like a modified Mercury Racing 2.5 Drag, which can make 400 hp on alcohol fuel, and you’ve got a real rocket.”

In keeping with the simple-is-best approach, UMPBA events do not utilize electronic timing. Boats approach a “commitment buoy” and a starting line buoy together, about 50 feet apart. Racers are then flagged off from a starting boat located 30 feet beyond the start buoy. Judges and a camera are waiting in a finish-line boat at the end of the 800-foot course. Each class runs a double-elimination format.

“If a competitor suspects the other racer broke out of the class speed limit, he can ask to see that racer’s GPS for verification,” said Seubert. “There is a 2 mph breakout for each class, so racers have that leeway before they break out and are disqualified.”

A new feature on the way for UMPBA races is a custom Ambush SS 1756 safety/tow boat being built by Legendcraft Boats of Alexander, Ark.,  for the organization. The boat will be powered by a Mercury Racing 60R outboard with tiller steering. The 17-foot aluminum boat will be equipped with dive tank racks and a step-off transom for the rescue divers stationed at each race. The boat will also be used to set the course and as a tow craft for disabled race boats, according to Seubert.

UMPBA’s new safety boat, a Legendcraft powered by 60R

The 60R outboard features a four-cylinder, 1.0-liter long-stroke powerhead tuned for torque by Mercury Racing. The WOT range is extended to 6300 rpm to maximize acceleration and enable more propping options. A single overhead camshaft cylinder head keeps the powerhead as light and slim as possible for less intrusion on the transom. The high-thrust gearcase accommodates a robust 2.33:1 ratio to handle up to 20 percent more prop-blade area than a standard gearcase, and is shaped to provide added lift aft to further boost hole-shot performance and confident handling at speed.

Racing’s new 60R is ready for action on race day

“Legendcraft is has built the boat, and it was rigged by Merten Marine in Oshkosh, Wis., which has been very supportive of the UMPBA,” said Seubert. “The boat will showcase the new Mercury Racing 60R outboard, and this will be the first 60R to be equipped with tiller steering.”

Jim Merten rigs the new safety boat

The UMPBA has four events on its 2020 schedule, and has been able to hold the first two by observing social distancing and other pandemic precautions at its races. Drag boat racing is very popular in the southern United States – the Outboard Drag Boat Association holds its annual championships at Jasper, Tenn., in October – and racers from that region and from as far away as New York State have travelled to race with the UMPBA.

“What I enjoy most about the UMPBA is that the racing is competitive, but not cut-throat,” said Petersen. “It’s designed to be safe, stress-free and a lot of fun.”

Sounds like the perfect way for a Mercury Racing fan to experience the Wide Open lifestyle.

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Hydrodynamics: Part 2 – The Science and Art of Gearcase Hydrodynamics

In our recent Intro to Hydrodynamics post we discussed the impact of drag on escalating boat speed, and the importance of using the science of hydrodynamics to reduce that drag. The gearcase is the one component of a high-performance sterndrive or outboard that is always in the water, and thus subject to drag. Mercury Marine and Mercury Racing have a long history of developing gearcases for racing and high-performance applications, with the first Quicksilver racing gearcase and shortened midsection introduced in 1950 for the Kiekhaefer Mercury KG-7 Super 10 Hurricane outboard, which promised to increase top speed by 20 to 30 percent on the racing runabouts of the era.

Drive development has a long history at Mercury Racing

Today, Mercury Racing engineers face some of the same challenges that complicated gearcase design 70 years ago. One is the trade-off between robust internal design – to handle ever-increasing power – and the desire to create a slim shape that’s as hydrodynamic as possible. All of the design work starts in the computer.

“We begin with some basic parameters – pinion and driven gear diameters, bearing sizes, and max prop diameter – this sets the propshaft-to-anti-ventilation plate dimension,” explains Jeff Broman, Mercury Racing Director of Engineering. “Then we have some basic configuration decisions around the shifting mechanism, which could be in the gearcase or further up the driveline, whether the exhaust will be through-prop or above-water and water inlets will be in the gearcase or on the transom, and the choice of single- or dual-pinion drive shaft.”

Sport Master Gearcase Cutaway

Once those mechanical parameters have been defined, engineers can start wrapping a hydrodynamic housing around the internal parts. The initial shape starts with established rules-of-thumb based on years of design experience. These relate to making a housing that has low drag, good handling characteristics, and resists cavitation, but also is able to be consistently and precisely manufactured, taking into account casting process capabilities and reasonable machining tolerances.

The anticipated boat speed then sets the shape of the torpedo – higher speeds require more length for a given diameter. Operating speed also defines the shape of the skeg, which is especially critical on surfacing drives. When a surfacing drive is running at speed, only the skeg is in the water, so the design of the skeg is critical to maintaining stability. The shape of the torpedo is also extremely important, particularly during re-entry and when accelerating onto plane. The torpedo also controls how the water flows into the prop. It is important to have a smooth flow of water up and around the gearcase, controlling the amount of lift generated. Outboard gearcases present the additional challenge of designing water pickups, which must be located and shaped based on the operating speed, minimizing sensitivity to trim and debris fouling and always providing enough cooling water to the engine.

Example of M6 / M8 Drive Overlay

Once an initial housing designed, it goes into CFD (computational fluid dynamics) simulation, which is the numerical analysis of fluid flow accomplished in powerful computers. Mercury continues to develop its proprietary methods and capabilities in this field. Current cutting-edge CFD simulations can capture air mixed with water – critical on surfacing drives like the Sport Master, M6, and M8 – and incorporates a moving propeller. The simulation offers guidance in refining the design.

1965 Speedmaster Assembly Drawing

The next step is the creation of a prototype, which may be a modification of a current gearcase or a new shape completely machined from billet. Then it’s time to head for the water. Depending on the application, in-water evaluation may start with a boat in the Mercury fleet. If an appropriate boat is not available, Mercury Racing will partner with a boat builder to gain access to a boat. Testing of a new gearcase housing is guided by Mercury Racing hydrodynamics specialist, Mike Griffiths. Griffiths has years of experience in all types of high-speed boats and has the expertise to safely evaluate any aspect of boat setup. He will put the new gearcase through a series of tests to evaluate how it will work in a real application. The output of these tests is a mix of objective data – top speed, acceleration, steering loads, and water pressure – and his subjective “feel” of the boat. Based on those tests, engineers will continue to fine tune the design until it meets Mercury Racing standards.

“While speed is always a goal, it’s actually more important that the drive behaves in a safe and predictable manner,” said Broman. “Once we meet all of the design objectives, we release the new design for production.”

The result is the kind of Wide Open performance boat owners have come to expect from Mercury Racing – the ability to enjoy the absolute thrill of speed on the water with confidence and reliability.

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