EFI components easily reinstall on baseplate of SVS housing.

SO, DOES IT WORK?

Unequivocally, yes. We first tested the SVS system on a stock 1996 Mercury 225, mounted on a Gambler bass boat. The Gambler is a true high-performance hull, drawing its origins from HydroStream, Laser and other notable hall of fame outboard contenders. Though it features a bass fishing deck, this hull is a good representative of typical modern performance vee-bottom pad boats, and so provides a suitable test platform for the 225.

To find out what difference the SVS made horsepowerwise, we strapped on a Land & Sea Dynomite propeller shaft dynamometer. This nifty unit should be standard equipment for every marine dealer, as it allows not only troubleshooting without a lake nearby, but also provides hot-rodders with a way to test their mods to see what changes can result. In our case, the SVS bolt-on was a clear winner on the dyno. Without the SVS, peak horsepower came between 5,000 and 5,900 rpm, where the numbers hovered between 241 and 243 horses. Peak torque, at 272 foot-pounds, occurred between 4,100 and 4,400 rpm. The engine was completely stock except for the addition of Boyesen reeds.

Completed installation still allows for stock placement of fuel pump and vapor separator housing.

Later that afternoon, we again fired up the dyno with the SVS installed on the 225. The effect was noticeable immediately, as the big three-liter pulled a healthy 274 horsepower at 5,500 to 5,700 rpm. That's an increase of 31 horsepower, at the same rpm! Though the powerband narrowed somewhat, it was still an easy curve to prop for. Peak torque also increased, to 297 foot-pounds at 4,400 rpm.

OUT AT THE LAKE

Does the increased dyno horsepower translate to more speed on the water? We trailered the Gambler to a nearby lake to find out. On the water with a 190-pound driver and 230-pound passenger, three batteries, a trolling motor and approximately 100 pounds of assorted loose gear, we tested the rig with and without the SVS. Since it was already installed on the engine, the easy way to simulate the stock setup was to simply disconnect the SVS's linkage. That way, the slide assembly would stay shut and the engine would receive the same amount of airflow as it would with the stock plenum cover.

Front view of SVS-equipped three-liter Merc gives a menacing look.

With a 26-inch-pitch Trophy four-blade prop, the Gambler hit a best top speed of 74.4 mph at 5,750 rpm, measured on a handheld GPS unit and backed up by a calibrated Gaffrig speedometer and tach. Four runs were averaged to obtain the top-end readings. Zero-to-30 mph times averaged a slow 11.3 seconds (bass boats are typically not noted for blazing holeshots, due to the aft-weighted hull balance). Getting to 60 mph required 21.4 seconds from a dead stop. Midrange punch was slow, taking 11.2 seconds to accelerate from 30 to 60 mph and 15.7 seconds to go from 40 to 70.

After these runs were recorded, we removed the hood and reconnected the SVS linkage to have another go. This time, top speeds rose to 78.6 mph at 6,050 rpm, for a net gain of slightly over four miles per hour and 300 rpm. The added punch was easily felt in the seat and measured on the stopwatch. Idle to 30 mph now took just 9.5 seconds, a savings of over two ticks on the clock. Getting to 60 now took three seconds less than before, checking in at 18.3 seconds.

Midrange punch was also tighter, as the SVS shaved over two seconds from both the 30-60 and 40-70 runs. For grins, we bolted on a 27-inch Tempest propeller and recorded top speeds of 78 mph at 5,800 rpm (stock ) and 81.6 mph at 6,050 rpm (with SVS).