The trim will only go down when the engine is running or immediately after charging the cranking battery.  Tested the cranking battery and its fine.  I also switched the relays with no success.  Can anyone give me some other things to try? This is my first boat so i'm kinda new to this....Thnx.

Check the switch with an volt /ohm meter.  You can buy a cheep analog one at Walmart for $5.  Three wires should run from the switch to the relays.  There should be three positions for the switch.  

1 Up

2 Off

3 Down

To lift the outboard, the switch connects the common usually center terminal to the UP wire.  To lower the outboard the swich connects the common to the Down Wire.  Usually 12V is connected to the common and you connect the 12V to the UP relay or the down relay depending on which way you move the switch.  If your switch is in the dash, checking and replacing it is easy.  If it is in the handle, replacing it may be more difficult.

Disconnect the wires from the relay and put an ohm meter across every combinations of wires and each should be open (not connected).

1 and 2    Open

1 and 3    Open

2 and 3    Open

Repeat the test each time and flip the switch up and down with the meter measuring the wires and you should get a short (zero ohms) across two sets of wires

1 and 2  Open up, Open off, Short down

1 and 3  Open up, Open off, open down

2 and 3  Short up, Open off, open down

If all of this checks out, the switch is fine.  The next thing to check is the connections from the tilt and trim motor to the battery.  If the connections are loose, corroded or damaged, you will have trouble getting enough current to the motor to lift it.  You can put a volt meter across the positve wire from the tilt motor to the battery terminal and measure the voltage drop when you lift the motor.  If it is a few volts you have a problem somewhere in that line or the connections.  Repeat the test on both ends of the negative wire and if it has a voltage drop of a few volts you probably have a problem with that wire or connections.  

If I had to guess, you have a loose or corroded connection somewhere in your system.  As long as the battery is charged, you can overcome the large voltage drop that is occurring somewhere.  Try these things out and let us know what you find.