When you take a stroll down your local marina's charter docks, oohing and aahing over the 50-plus-foot custom-built sport-fishers bobbing gently at their moorings, keep in mind that boats of this caliber haven't been around for very long. The main factor driving the existence of the big, roomy sport-fishers built today is the research and innovations in marine power that have occurred over the last 30 years.
"In the early 1960s, 90 percent of the charter boats fishing out of Oregon Inlet were single-screw boats with gasoline engines," says Buddy Davis of Davis Boatworks, "with most of those in the 30- to 35-foot range and the biggest ones only reaching about 40 feet." The only diesel engines suitable for marine power at that time were the 190-hp Gray Marine diesels - WWII surplus engines used to power landing craft. These Grays later evolved into the GM (and later the Detroit) 671. "You could run the old Gray on the pins all day, but not the gas engines. If you ran the gas engines like that they wouldn't last, so you had to pull them back, resulting in about the same amount of usable horsepower as the diesels," says Davis.
What was needed for diesels to become a viable marine power source was lots of horsepower in a smaller package. "Man will always strive to go faster in whatever he's sitting in, and that takes horsepower," says Sonny Hines, builder of Hines-Farley Yachts in Virginia. Hines saw the move toward high-horsepower, small-footprint marine diesels take off in the early 1970s when companies like Johnson & Towers, Stuart Stephens and Covington started "reconditioning" diesel engines from Detroit and Caterpillar. "These small companies were the leaders in squeezing more horsepower out of the engines. They were really just tearing them down and then doing whatever it took to hop them up," he says.
Since the marine market represented just a fraction of their business in the mid- to late 1960s, big companies like Detroit and Caterpillar were happy to let the after-market companies put a lot of research into boosting the horsepower in diesels for marine use, says Hines. "I imagine that they learned a lot from those small aftermarket companies," he says.
The result: Engines like the Detroit 671 went from producing 190 hp in the early '60s to 300 hp by the end of the decade - from the same size block.
"Five years ago we really didn't have an engine for sport-fishing yachts of this size," says Hines. "The introduction of the Detroit 2000 series -- with its incredibly high horsepower in such a small package - is the reason more 70-foot boats are showing up on the dock."
One of the main innovations used to boost horsepower in diesels without significantly increasing their size was the successful application of turbo charging. Turbo-charged diesel engines existed in the '50s and '60s, but early models had a reputation for failure. It wasn't until the mid- to late '70s that reliable turbo-powered engines started making their mark in the marine power industry.
Turbo charging an engine is really quite simple in theory: Use a turbo fan to force compressed air into the combustion chamber. Since compressed air is more condensed, it contains more molecules of oxygen, which means it can sustain the burning of more fuel, thus increasing horsepower. The only problem is, when you compress air you heat it up. And since anything that's hotter starts to expand, turbo-chargers become less efficient the hotter the air gets.
This problem fueled the use of after-cooled engines in the mid- to late '70s. After-cooling runs the hot, compressed air through a heat exchanger filled with seawater to cool it, making it more dense and packing an even greater amount of oxygen into a given volume. "You can expect a 50- to 75-percent increase in horsepower when using a turbo-charger and after-cooler over a naturally aspirated engine built on the same block," says Dave Stevens of MAN engines.
Another of the more recent innovations in marine power to take the industry by storm has been the advent of electronic controls, says Gene Wineland of Caterpillar Marine. "Electronically controlled engines control the amount of fuel going to the injectors at all loads, ensuring maximum efficiency throughout their throttle range. Mechanical engines have to be set to run optimally at one point," says Wineland. Through this efficient monitoring of fuel flow, electronic controls minimize smoke, increase fuel economy and lower harmful emissions.
"It kind of slowly followed the advent of electronic controls in automobiles," Davis says. "Engines started changing in the mid-'80s from mechanical to electronic controls and became much more efficient. Nowadays if you want to fix something, you have to bring a laptop computer to the boat. I could pull a head as a boy, but now I can't pull off a valve cover."
It also has to be said that a dramatic weight reduction in engine and boatbuilding materials has increased the performance of sport-fishing boats considerably. "In the early '70s if you could get 20 knots out of a boat - that was a fast boat," Hines says. "Today, most want a boat that will run between 35 and 40 knots. And you need to keep the boat light in order to reach those speeds. Years ago we didn't know how to build a lightweight boat that could go fast. If you drove them too fast, they would come apart. Then we'd add more glass to hold them together, which of course added more weight. Now we can build boats with new composites and resins that make the boats lighter and stronger."
