Yamaha T8 tilt & trim problem

[pike hunter]

I have a problem with the power tilt & trim on my T8 but only when it's cold. When I activate the switch, the pump is running but the motor is not moving either up or down but after I activate the pump on & off rapidly then it start to work up & down.

I was thinking of changing the pump oil and add some fresh one but I don't know how to drain the old one and how to fill-up the new one.
Thank's for you're help