Testing The Pro Control Unit

The Brucato Pro Control Unit yielded a top speed of 128.9 MPH, which was a 4.7 MPH gain over the Mercury digital ECU.

The results of our adjustments were impressive.  Acceleration was greatly improved throughout the entire RPM range, while fuel consumption was noticeably reduced at cruising speeds.  We made use of the Acceleration Compensation feature, which allows the adjustment of fuel delivery during acceleration only.  To take this a step further, experiment with the sensitivity knob, which determines how much the throttle must be moved to deliver the extra fuel.

One of our first impressions with the PCU that became immediately apparent was the improvement in acceleration.  This should not be surprising, since the PCU can offer a level of progressive adjustability that the Mercury ECU is incapable of.  Remember, the Mercury ECU can offer a single, linear adjustment of the fuel curve, whereas the PCU allows the user to adjust the fuel curve in 500-RPM increments all the way up to the rev limit.  The difference was indeed impressive, but there was more to go.  Further adjustment to acceleration compensation settings will yield even more gains - especially on a modified engine.

We had now fully adjusted the PCU’s fuel curve for all but full throttle operation.   The real fun was about to begin when we were setting up for the wide open throttle capabilities of this new fuel system.

With the serial data cable connected to the PCU, you can view and alter the entire fuel curve and set the rev limit.

You might remember from Part One of this series that the Part Throttle adjustment knob allows the user to adjust the fuel curve of the engine for anything below full throttle operation.  Why is the Part Throttle adjustment so useful?  There are several reasons;  The full throttle requirements of a high performance engine are different than that of part throttle operation.  For example, we might want a relatively lean mixture for bleeding-edge wide open throttle operation; however, a richer setting would be more desirable for cruising speeds.  Further, our part throttle fuel curve may serve different purposes.  Perhaps we might want to use the boat for water skiing, where the engine would be under a much greater load for extended periods of time.  Again, a slightly rich setting might be in order here, which would allow the engine to run cooler with less chance of detonation.

One thing that became apparent during initial testing was that the resulting power increase from the installation of the PCU was pushing us past our power band for this engine. This was never a problem with our Mercury A63 Digital ECU while turning the Mercury 14.5 x 32P Lab Cleaver. We were now exceeding 9000 RPM at WOT, and we had yet to test this rig with a light load.  We needed to step up to a larger propeller or change our lower unit gear ratio. This adds an additional variable to the equation, so we surmised that we would run tests in two stages, with two different lower units.

Stage one of the test would be under fully loaded conditions - two occupants weighing roughly 200 pounds each, and 28 gallons of fuel.  For this stage of testing, we would use the Sportmaster lower unit equipped with the 1.87:1 gear ratio.  Since we were very pleased with the performance and consistency of our Mercury 14 x 32P cleaver, It was decided that for the light-load solo runs, we would switch to a Sportmaster equipped with a 1.75:1 gear set.

Page Four: Performance Results