Posted by JRP on 02/12/16 - 5:41 AM
#44
tedious wrote:
I am still trying to find out whether the displacement gain on the 90 was created by going to an unsleeved block - does anyone know?
I also wonder where this trend of having motors with the same nominal horsepower and quite different actual horsepower is going to go. Is someone eventually going to be able to get a 9.9 that actually pushes out 40, so they can ski on lakes where there's a 10-horse limit? I predict the party is going to end when someone has an accident and successfully sues the manufacturer for putting out a motor whose actual power is significantly higher than the nameplate power.
Tim
I don't know whether the block is sleeved or not. Mercury collaborated with BMW in the design/enginering of this engine, so I expect it is well done regardless.
As for the power output, manufacturers are permitted a 10% variance in HP output from the nominal used for naming the model. So I don't think they are in any legal jeopardy there.
The reference to increased torque is more interesting to me. By re-mapping fuel delivery and timing, it's possible to increase the torque at a given rpm and/or widen the peak torque band of the engine without affecting the max HP rating. So this version of the 115 engine could offer a wider/deeper powerband than the other two that have been offered.
Incidentally, there are now three versions of the 115 CT. There is the "Fourstroke", the "SeaPro", and now this "ProXS Fourstroke". Studying the spec sheets for each of these variants, the only significant difference I notice is the peak horsepower rpm range: SeaPro, 5000-5500 rpm; FourStroke, 5000-6000 rpm; ProXS, 5300-6300 rpm.