Re: 1985 force 125 carb mixture screws
Power trim does not have a lock. The hydraulic advantage of the tilt cylinder keeps the engine from popping out of the water in reverse or upon slowing down rapidly. The tilt cylinder and the pump have release valves so if you hit something underway, the engine will pop up and gradually return to the water.
The trim is adjustable (obviously) so after dropping the engine off tilt, adjust it all the way in to take off and plane rapidly, then out as needed to get top speed. This will vary with hull and engine, and at some point you may get cavitation or ventilation. If you do, then you need to run it down a bit. Because of the release valves, these tilt/trim units will not support the tilted engine at anything above about 1500 RPM and the engine will bang down onto the trim cylinder ram (you called it a trim bar) if you try it
For trailering, you must use a trailering bar to keep the engine tilted. If you don't have one, a 2 X 4 wedged between the yoke and transom clamps will work BUT youmust secure it to keep it from dropping out as the engine moves a bit during trailering.
John may be thinking of some other compound: While there are some that do build-up and coat parts (intentionally), WD 40 does not turn to varnish. In fact, it is useful to remove these compounds. I use it all the time to clean carbs. Works very well and in some instances will remove varnish and old congealed oil without scrubbing.