How to best fill an OB power trim/tilt reservoir

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FOUNDER of Classic Parker Forum
Feb 16, 2006
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Newbury, MA
FYI ... posting this in case Tim needs to do a flush and fill ... plu its something else for the search archives.

To properly check the OB's trim/tilt fill, both the trim and tilt rams must be extended. Raise OB all the way up and set it on its mooring/full raise lock. If you cannot via the trim motor (you may be too low on fluid) then back off the manual release valve and with some extra help, raise the OB all the way up and LOCK it into place. Be safe, so engage the OB up locks or place some hardwood blocks in there so it doesn't drop on you :shock: ! Then re-tighten the manual release valve.

Tilt reservoirs are easier and best to fill IMHO when the boat is on a trailer, as you can lower the tongue all the way to the ground. The intent is to position the tilt/trim reservoir as straight up & down as you can get it. However, you can still do it as the boat is normally positioned, but you will need a helper ... you can't do this alone ... unless you have 3 hands. Your assistant will simply keep their finger on the trim/tilt UP button on the OB cowl for this entire procedure.

Trim the OB all the way up and engage the full UP tilt support (or use a block ... again, you're opening the hydraulics - you DO NOT want an OB to fall on any bodypart!). I use the small long/slender nozzle on the end of the recommended trim fluid container to help keep it in there, but some pros use empty ketchup bottles like you see at diners. I also use Walmarts $2 tube Powertech (?) t/t fluid as it is mil-spec 4606 (if I remember the spec# right) and it works great for this and in my Teleflex hydraulic steering pumps.

Now this is where your assistant comes in. Have them press the t/t UP button (they will not remove their finger until you teel them too ...) while you slowly open the t/t reservoir cap (allowing air to escape) and insert the trim fluid tube/nozzle. Then pump in as much fluid as it will take. Keep the UP button pressed even though the OB may already be up (maybe even off its supports). You will hear the t/t motor hit the bypass valve as the motor sound will change. Still add fluid until the t/t reservoir won't take any more fluid and it starts to drip/gush out. Mind you, your helper's finger is always on the UP button ... and while their finger is still pressing the UP button, quickly put the trim reservoir cap back on. You're all done :) - so they can stop holding the UP button now - whew!.

FYI - the concept behind holding the UP button allows the motor to "suck" in all the fluid it can while attempting to push the OB all the way up. Doing in this way you should not have to top off the system/reservoir again, even after purging, and hopefully not for a loooooong time afterward.

Note - OB trim/tilt systems are self-purging of any trapped air using this process. When bled of all air in the t/t system, you won't hear much if any bubbling or gurgling as the OB starts its up or down cycle, you should just hear a smooth start of the rams in motion. On OBs, Yams especially, if you hear squeaking during the trim/tilt cycle, lube the ends of the t/t rams.

I find that with the fluid adding regimen described above that I never have to top it off with more fluid after performing the purge cycles. But you should always perform these "purge cycles" anyway, even if you don't need to add any more fluid.

To purge the t/t system of air, remove the tilt lock or wood block and cycle the OB down by "jogging" it down, in 2-3 seconds bursts. Then rest the t/t motor 10 seconds (akin to NOT cranking on a starter motor continuously), and then cycle it UP all the way in one long run. Rest/pause again 10 seconds or more. Then repeat that complete down/up cycle 1 to 2 more times to ensure that it has bled all the air out of the t/t system.