Re: How to replace a rocker switch in throttle handle?
I recently had the very same problem you're describing. Didn't have a working multimeter handy, but I was able to rule out the switch on the throttle handle by reversing the "up" and "down" connections where the wiring from that switch connects to the harness. (You may or may not be able to do this, depending on your wiring harness.) The motor now trimmed down when I pressed "up" on the helm switch and did nothing when I pressed "down" -- which told me the switch on the throttle was fine and the problem was farther back. Turned out to be just a loose connection at the relay in the motor. Best of luck to you!
P.S. - Hope you enjoy your Blue Wave as much as I enjoy mine!