Mercury trim pump (1975) proper fluids

[CML]

I am resealing my 1975 mercury four line trim pump and I was wondering what the best fluid to run in it when I'm done. The pump says to run SAE 20W oil in it, but in regular hydro pumps they say motor oil rots the seals, so I was wondering if mercury trim oil would be better. Any help would be greatly appreciated.

 

[oldman570]

Re: Mercury trim pump (1975) proper fluids

Mercury trim oil would be fine. As the pump states a good 20 weight non detergent oil and automatic trans oil will work also on most tilt/trim systems. JMO
Oldman570

 

[CML]

Re: Mercury trim pump (1975) proper fluids

Thanks for your feedback. When I change types of oils is there anything I need to do to get the old oil out of the cylinders?

 

[Chris1956]

Re: Mercury trim pump (1975) proper fluids

Bleed the cylinders. Not sure I would recommend two kinds of oil be mixed.

BTW Merc recommended 5W-30 motor oil for my '77 merc IL6 4 hydraulic line PTT.

The Merc trim oil is likely Dextron ATF.

 

[CML]

Re: Mercury trim pump (1975) proper fluids

Thanks for all the info. I wasn't sure what oil was in it, seemed to be some sort of motor oil. It's my grandfather's boat and has become my project and he hadn't touched it in years so he doesn't know either. So I just wanted to try to get all the old oil out so hopefully it wouldn't be a mix, should I fill it with the new oil and drain it once to get it all out?

 

[Chris1956]

Re: Mercury trim pump (1975) proper fluids

I would open the lines at the control valve and run the pump motor until all the fluid is out of the pump/reservoir. Now refill the pump/reservoir and bleed the cylinders(up and down circuits), until you see new fluid.

 

[CML]

Re: Mercury trim pump (1975) proper fluids

Thanks for all the help.