2 stroke

i have a 2005 nitro 188 sport with a 115hp mercury 2 stroke. i have 3 motor trim locations on my boat: 1 on the bow; 1 on the throttle; and 1 on the motor itself. both the bow and the throttle work fine, in both directions, but the, motor trim, stopped trimming up only...it still trims...

I just bought this boat a little over a month ago and have taken it out 4 times or so. Its not my first boat.. so I'm experienced with getting boats on plane.. but damn this boat is a tuff one! this is 20' 2" and paired with the Mercury 225 Dfi (3.0l).. Currently I'm replacing spark plugs...