Power trim goes down on my Merc 90 when I start going and I can not trim up the motor while moving. The fluid level is full and the motor is new and help would be great??

check oil level in reservoir

The tilt and trim fluid reservoir for a 2006 Evinrude 90hp motor is typically located on the side of the tilt and trim unit, near the bottom of the motor. It may be a small plastic or metal container with a screw cap or plug. To add fluid, first, ensure the motor is in the full tilt-up position and that the tilt and trim system is not in operation. Then, remove the screw cap or plug and add hydraulic fluid until it reaches the full mark on the dipstick or sight glass. Use the recommended fluid type specified in the owner's manual or on the reservoir cap. Finally, replace the screw cap or plug and wipe away any excess fluid. It's recommended to check the fluid level periodically and add more fluid as necessary.

you have air lock try draining some out maybe put some weight on drive or take lines off and add fluid till you see it come out you have to bleed air out like brakes

Low fluid level will cause it to fail to actuate and not go up or down, can also let it not hold position as well. Filling to proper leevel with specified lubricant is recommended. If you allow the level to go too low, the pump will pull air and could burn out.

You raise the front of the car & support it if necessary,
to put a bottle under it,such as an old washer fluid bottle

Then remove the steering pump return hose from the fluid
container

Put that hose into some plastic tubing & into the empty bottle

Remove the injector fuses, so the motor gets no fuel

Crank the motor & the old fluid goes into the bottle


Add new fluid Dex/Merc or Mercon V to make sure the
container has fluid as you flush out the old

When done,return the return hose,clean up & start the motor
Turn wheels lock to lock a couple times,put it on the ground
& check the fluid level

Change trans & power steering every 3 years or they will
fail for sure.

Those two fluids will not remove heat after 2 or 3 years
in service.

should go down if you are trimming down ,

There? are two trim relays Themba look like squsre black switches Get two new and fit!! Should solve your Problem.:,

Let me preface this by saying I'm not trying to insult you.. I just don't know you level of understanding of the trim unit so I'm starting simple.....

First, these are normally a hydraulic system. Did you check the hydraulic fluid level to ensure it's full?

Second: The ram (what raises/lowers the engine) has seals in it. Have you checked to make sure you do not have a leak in the seal where the ram goes in and out? If there is a leak, the piston will just push fluid/air out and not have enough pressure to lift the engine.

Third: Is the shaft coming out of the ram nice and shiny and not rusted? I have seen them rust/fuse to the housing and fail to go in/out when the switch is activated to raise/lower the motor. A few good soakings over a couple of days with a product like PB Blaster should free it up. Make sure to lube the shaft regularly through the season, at the end of the season and after storage if it's not used in the winter months.

Fourth (forgive me for even mentioning it) do you have a trim/tilt lock on the engine? Many outboards have a lock on them so you can lock it while trailering/storing it and take the pressure off the hydraulic pump/ram. Hopefully this will get you pointed in the right direction.