Need to look at page 1c-14 of the Mercruiser #14 service manual.
See:
http://www.boatfix.com/merc/Servmanl/14/14c1.pdf
There's some good troubleshooting tips in chapter 1c and a wiring diagram for the trim on page 1c-16.
It can't be the fuse since the motor runs in the down mode.
If you need to transport the boat and must raise the drive, take the plastic covers and nuts off the trim cylinder stern ends to free the drive from the cylinders, lift the drive and strap it up with line or nylon straps. Alternatively, there's only a few more steps involved to pull the drive off the bellhousing now that the trim cylinders are loose (sure makes lubing the coupler a breeze)... See:
http://www.boatfix.com/merc/Servmanl/14/14a2.pdf
The entire manual is here:
http://www.boatfix.com/merc/Servmanl/14/14notice.pdf