Need to know a couple of things...
1. How old is your 115? Honda made two different models. The alarms work a little differently on each. Most likely, you have the more recent model, since the older model ECM did not recognize when the motor was put into gear....or you have a wiring issue.
2. What warning lights are on or off. You should have four warning lights. Red (overheat), Green (oil pressure), and two motor (generally red...check engine and charge light). W
3. When you turn the key switch to on, do you get two beeps of the alarm? Do all the warning lights come on for two seconds?
4. Is the beeping a solid beep or is it a beep, beep, beep?
5. Did you see this motor run before you bought it and before you installed it?
Mike