Filling: To properly check the fill, the trim/tilt rams must be extended. Raise OB all the way up (if you can't via the trim motor, then back off the manual release valve and with extra help, tilt/raise the OB all the way up and set it on its mooring/full raise lock, then re-tighten the release valve).

Tilt reservoirs are easier and best to fill when the boat is on a trailer, as you can lower the tongue all the way to the ground. You want the tilt/trim reservoir as vertical as you can get it. This procedure is also best done with a helper to assist you, as they will keep their finger on the t/t UP button on the OB cowl, when needed.

Trim the OB all the way up and engage the full-up tilt support (or use a block ... you do NOT want an OB to fall on any bodypart !). Slowly open the t/t reservoir cap (allowing air to escape) and insert the trim fluid** tube/nozzle. I use a 60cc syringe with a clear tube attached. (I don't use an assistant, but for this post I will include those instructions.)
Now this is where your assistant comes in. Have them press the t/t UP button as you put in ALL the fluid it will take. Keep pressing UP while the OB goes all the way up (off its supports), you will hear the t/t motor hit the bypass valve (the motor sound will change) and until the t/t reservoir won't take any more fluid and it starts to drip or push out. Remember, your helper's finger is still ON the UP button ... so quickly put the trim reservoir cap back on. All done!

The concept behind "holding the UP button while filling" allows the trim motor to suck up all of the fluid it can via the hydraulic system. Doing it in this manner, you should not have to top off the reservoir again, hopefully for a long time.

Bleeding: OB tilt/trim units are "self-bleeding" and you should always perform these "purge cycles" even if you don't need to add any more fluid. To purge/check, remove the tilt lock (if engaged) and cycle the OB down by "jogging" it down, in 3 second bursts. Then rest the motor about 15 seconds. Repeat until all the way down. Then raise it UP all the way in one long blast.

Rest/pause again ... 30 seconds or more ... then repeat that complete cycle a few more times to ensure that it has bled all the air out of the t/t system. When bled of all air, you won't hear bubbling or gurgling as the OB starts its up or down cycle ... you should just hear a smooth start of the rams in motion.

When I re-assemble the units, I fill the system up as high as I can with the trim caps off. Then screw those down. Now, with the rods fully extended, fill the reservoir all the way up to the bottom of the threads on the fill plug. Screw on the cap. Cycle it up and down a few times and then raise it all the way to the top again. Let it sit for a few minutes, then stow the OB onto your towing bar. All done.

**I have always insisted on using Yamaha T & T fluid instead of Dexron II. Now that Dexron II is not available anymore (it is now a blended fluid and will foam some) I only recommend Yamaha T&T fluid.