posted 06-15-2015 09:26 AM ET (US)

The E-TEC engine provides data about a parameter called LOAD which represents the throttle position on a scale of 0 to 100. I developed the following table of data from some observations I made of boat speed and LOAD. I assumed at maximum throttle and maximum boat speed the engine was delivering its rated power, 225-HP. At other throttle settings I deduced the horsepower by comparing the boat speed at a particular LOAD setting with the FULL throttle boat speed, and calculated the horsepower as a function of boat speed, based on the general concept that boat speed is proportional the the power-to-weight ratio to the 0.5 exponent. That is a reasonable assumption for a moderate speed planing hull boat. Here is the dataLOAD HP

37 111.1

39 126.8

42 142.6

46 168.6

52 196.8

58 212.0

96 225.0

If you plot this data, the plot looks quite linear, except for the LOAD = 96 point. This suggests to me that probably the engine hit maximum power somewhere less than LOAD = 96.

Here is a plot:

From the data in the region of 37 < LOAD < 58, that is, the center portion of the LOAD range, it appears that one could predict the horsepower by the following relationship:

HP = Full-ThrottleHP x ( (0.025 x LOAD) - 0.425)

Testing that function at LOAD = 42 and Full-ThrottleHP = 225:

HP = 225 x ( (0.025 x 42) - 0.425)

HP = 140