90+ MPH with a 2-Liter Merc — Here’s How
Horsepower equals speed, that’s a formula high performance boaters have been relying on since the invention of the internal combustion engine and the propeller. And in most cases, the easiest way to increase top speed and improve acceleration is to add more power. But there’s also a sign that hangs in almost every speed shop, “horsepower costs money, how fast do you want to go?”
Elsewhere in this issue, you’ll read about the results from the 2009 Enduro 300 at Parker, Arizona. And true to its roots, the 300 embraces almost any kind of boat and engine combination thanks to its unique class structure. The entrants in this race run the gamut from 1200 horsepower supercharged inboards to under 100 c.i. displacement 2-strokes.
One of the most popular and competitive classes in recent years has been Division III, primarily for Mod VP style outboards with engines under 130 cubic inches. In fact, a couple of the overall race winners have emerged from this Division thanks to longevity and the ability to extract a lot of miles per hour out of a rather small displacement outboard pushing an air-entrapment style hull.
One of the true masters at making a Mod VP run with the much bigger dogs is Al Stoker of John’s Custom Marine in Stanton, California, both a participant and a sponsor of this year’s Enduro 300. If you need credentials, Al’s resume is as long as any one in the sport, winner of numerous Mod VP marathons since the 1970s like the Lake Havasu Outboard World Championships, the Parker 7-Hour and a host of other titles from coast to coast.
Al’s ride for the 2009 Enduro is a collaboration with his long-time friend and customer, Fred Bowden, California Gold Racing. The hull is a 1987 Stoker 20 SST of which Fred is the proud fourth owner. Rumor has it that the boat at sometime in the past was actually filled with dirt and made into a flower planter before it was rescued to race again. The motor is a vintage SST-120 Merc (2-liter, 122 c.i.) that’s definitely got some hours on it. When it came from the factory it was rated at 180 horsepower at the propshaft @ 7,500 rpm.
Fred turned the boat and motor over to Al and said, “get it ready”. Division III tech rules say that the boat, engine and rigging (less fuel and driver) has to tip the scales no lighter than 1,325 pounds. In order to make weight, about 80 pounds of ballast was secured under the center mounted 60 gallon fuel tank. Also a class rule is the requirement that the engine be hung so the propshaft must be at least one-inch below the bottom of the hull. The Merc has a standard 15-inch mid-section and a Sportmaster lower unit with 1.87:1 gear ratio.
As a matter of precaution, Al disassembled the engine, checked out the condition of the stock 2-ring pistons, bearings, rods, crank and carbon fiber reeds. The rotating parts have been balanced and a little clean-up done to the ports. The carburetors have to stay one-hundred percent stock with a 1.327″ bore spec.
As part of his routine preparation ritual, Al is meticulous about the rigging and Loctiting or Nylocing every last nut and bolt in the boat. Where “oversized” can be used, it is, including the 9/16″ bolts securing the adjustable transom jackplate.
Al’s goal was to get the Stoker over the 90 mph mark given the confines of the set-up. “If I was allowed to take some weight out of the boat and raise the motor, it would run even better,” said Al. “But I’m happy with the results. We’ll do a little more prop testing in the 24 and 26 pitch range (round ear 3-blade, chopper style) to find just the right combination. We’ll be on the race course competing with boats that have more than five or six times as much horsepower as we do. They probably have more invested in chrome and anodizing alone than we do in this entire rig.”