as others have said, your assuming the switch on the throttle is bad when in fact the solenoid switch or both ( up/down) located on the trim pump housing at the stern might be bad... or the trim pump itself might be toast.. test the pump by manually jumping wires from your battery directly to the trim pump switches, there's two of them,, after you have grounded, touch pos wire to blue- "sky" usually operates trim up, then same for green, "grass" ie- down, usually will lower the unit.... if both work, then u know the pump is good... if you have gotten that far, then thouroughly clean your exsisting connections, it might work just fine... gunk and corrosion wont allow electrical charges to pass very well, after clean up if no go, then someplace between the pump and the throttle might have a bad wire.. or connection at throttle might be bad.. good luck.
Stony gave u the best advise thus far,, IMHO, start there.... id bet in most cases something is loose...