I frankly would not recommend the 115 E-TEC because it's gained so much weight that it's not really that much lighter than the 150. (I think they're now using the V-6 lower unit.) It also has the 2-position exhaust valve which adds complexity, and the V-6 is a bit smoother at low speed with 2 extra cylinders. With comparable loads, I don't think you'll see that much difference in fuel burn between the two motors, since the V-4 will be running with more throttle opening. The V-4 is a more "souped up" motor with higher HP/cu. in., so it tends to be a bit peakier, and comes on strong about 4000 rpm when the exhaust valve switches to the shorter exhaust passage. The V-6 has a flatter torque curve, so it's pretty happy between about 3200 rpm on up to WOT, although it feels like it's nearly vertical between about 1800 and 3000 rpm when it's switches to the very lean stratified charge mode to the homogeneous mode. It's sweet spot and peak torque is about 3700-3800 rpm at 27-28 mph and 6.5-7.0 gph. Tried attaching the torque curve pdf file to this but it's too big; if you pm me an email address I can send it to you.
Capt. Terry ran a couple of 150 Mercs on his Seafari before going with the E-TEC, so he can give you a good comparison with your current motor. Since likes to wake board at about 3000 rpm or less, he might even say that the E-TEC almost has too much torque! If you like the performance with your current motor, you may be disappointed with the lack of torque of the smaller motors.
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