Need for bleeding air from tilt/trim

[erie_guy]

My son's "new to us" 1976 mercury 80 hp engine has a four hose tilt and trim that we have been able to refurbish at minimum expense. However the hydraulic system has much for us to still understand. The engine tilts OK now and the pump/motor appear strong. But when to bleed entrained air is poorly described in the manual we have.

When initially charging the system with oil, it took several fillings of the reservoir to purge the air from the two cylinders and even then - it appeared foamy when we stopped bleeding. The cylinders had to be unbolted from the engine for this step and rotated so the bleeds were up. The tilt works well, and we wonder if the foam will eventually go away and any bubbles will end up in the reservoir - resulting in some future oil additions?

Sure would like to hear some real world experiences with this or similar tilt systems.

Thank for your help and happy boating !!

erie_guy
Port Clinton, OH

 

[Wingedwheel]

Re: Need for bleeding air from tilt/trim

I have the same system you're describing and to my knowledge they are self-bleeding. I've replaced the lines and just re-filled, ran the motor up and down a few times and topped the reservoir off. Never had a problem.

 

[erie_guy]

Re: Need for bleeding air from tilt/trim

WW,
Thanks for the insight. We will just top off the reservoir to assure we have not lost too much oil. Removing the cylinders each time to bleed definately would have been a pain.

erie_guy

 

[Chris1956]

Re: Need for bleeding air from tilt/trim

Erie-Guy, Those PTT units are not self bleeding. You have described the correct bleed procedure. I recommend you continue bleeding that way. Let the cylinders rest, bleed screw up for several minutes to allow the air to bubble out, prior to resuming the bleeding. Bleed one cylinder at a time, and run the PTT motor to force out some oil and the air.

BTW those PTT units were originally designed for 5W-30 motor oil. You may use ATF, if you like but don't mix.

 

[Wingedwheel]

Re: Need for bleeding air from tilt/trim

Chris, which model unit are you referring to? All my literature states "self-bleeding" and mine seems to have worked ok.

 

[Chris1956]

Re: Need for bleeding air from tilt/trim

Wing, I had a '77 Merc 1500 for many years. Both the Merc Service manual and the owners manual (if you can believe it) gave the bleeding procedure, as I have described it many times, on this forum. I am presuming the '76 Merc 800 has the same PTT unit.

 

[erie_guy]

Re: Need for bleeding air from tilt/trim

Chris

Thanks for the advice. We will check oil level in the reservoir - adding makeup 5w-30when needed. If we get into problems that appear to be related to air entrainment, we will pull the cylinders off so they can be bled individually.

erie_guy

 

[monk-monk]

Re: Need for bleeding air from tilt/trim

The PT&T system you have does require beeding...rams turned upward (inverted)...now, if you bleed the system and you still have foam (observe the fluid in the reservoir) then it's quite possible the "valve body can" has become dislodged from its position inside the reservoir...the "can" sits down over the filter screen and prevents the fluid exchange from reaching the surface of the reservoir abruptly...causing a foaming action...

 

[erie_guy]

Re: Need for bleeding air from tilt/trim

Thanks guys for all your help.

monk, you are correct I did pull the loose "can" from the reservoir as it seemed to inhibit proper oil flow. Next time in there, I will reinstall same.

Thank for all the advice. Time to go boating- the sun is out !!

erie_guy
Port Clinton, OH

 

[monk-monk]

Re: Need for bleeding air from tilt/trim

Yeah, gotta have that can in there...they are still available...and no, they don't fit too tight! When i come across one that doesn't fit snug enough, i SLIGHTLY flare the open end outwards at a few spots with needle nosed pliers...seems to help it grab that little lip in there around the screen..

 

[Wingedwheel]

Re: Need for bleeding air from tilt/trim

OK, I regress. I went back to my manual and Monk was right. I can't recall which literature I read that stated it was self-bleeding, but I didn't have any problems when I replaced on of my cylinders. so I assumed it was self bleeding. I guess I got lucky and sorry for any bad info I gave.