How do you drain fluid on an external tilt pump?

[69MyWay]

I have a 1979 vintage external hydraulic pump for the tilt/trim on my mercury outboard. The fluid is nasty and it won't hold a tilt position. It will sink down over time. WHen I had the motor off I drained all I could out of the system by actuating the rams and from what came out of the lines when I unhooked them from the unit. However, there is still quite a bit in there. I refilled with hydraulic fluid (like power steering fluid) as I was going to use it to flush..but I don't see a place to drain it.

My hope is I can cycle some good fluid through and get better performance.

????????

[riverrunner114]

they don't have a easy way to 'drain' them, you can back off on the bypass screw on the starboard side mounting bracket and let it drain. close it off, refill it and repeat untill its flushed out. doesn't completely drain it, but is the easiest way I know of to do what your needing.. good luck, john

[M.CHAPMAN]

John,
I believe he has the older model external pump that's mounted in the boat. You can remove the pump from the mounting bracket and remove the reservoir from the bottom and dump it. Clean it while you have it off. Reinstall and fill and bleed air. This may help.
-Michael

[riverrunner114]

John,
I believe he has the older model external pump that's mounted in the boat. You can remove the pump from the mounting bracket and remove the reservoir from the bottom and dump it. Clean it while you have it off. Reinstall and fill and bleed air. This may help.
-Michael

yes, you are right MC, I missed the word "external". thank you sir. I just had to clean my external pump for my jack plate and thats how I had to do it.. some dummie left the plug in the boat and let it get enough water to submerge my resevoir....:) . also after I purged the resevoir and refilled, I left one line loose and ran my new clean oil thru the cyl and lines to clean them out as well. you have to do one line loose, then the other.. john

[69MyWay]

Does it it take oil (like 40 weight), or hydraulic fluid? It seems to me I saw a note somewhere about 10/40, but my personal past experience has all hydraulic type things running hydraulic fluid.

Pulling and draining is not a big deal, but obviously a lot more steps than a "simple" drain plug. I guess it is like a lot of GM automatic transmissions. No drain plug there either...so you have to drop the pan to get the fluid out.

[riverrunner114]

I run 30 wt non-detergent in mine, but have seen people run either, just don't mix them. john