Re: power tilt and trim on 1979 Mercury 90hp outboard 6 cyl
If its an external pump and it won't turn you probly just need to put new brushes in the motor. They are available at any merc dealer for around $10.00. Put a scratch on the top and bottom of the motor so you can line it back up the same with the end cap and the pump housing. Remove the 2 screws on the end of the motor and carefully lift off the end cap ... there are your brushes

If the commutater (the copper surface the brushes ride on) is out of round or in bad shape clean it up in a lathe or put the armature in a drill and and use sand paper to make it look like new again ... if you just change the brushes and dont clean up the commutater it will just eat your new brushes.<br /><br />Or mabie your motor turns and the rams dont move??<br />Jon