'69 mercruiser hydraulic hose replacement

[strebor71]

Hi all, first post here. i have ordered and recieved a new trim hose for my 1969 mercuiser 120hp i/o. trim stopped working turned out the old hose was all coroded and leaking oil. question is, how do i go about replacing the old hose? i have removed the old one (to make sure i got the correct one ordered. all of the fluid that was in there is gone, and might be water in there? i assume that first i install the new one, but then what? what are the steps to re-filling the hydraulic fluid, and what type of fluid do i use, do i have to use a special tilt trim fluid from the marina parts dept. or can i use some type of auto tranny fluid? i am mostly confused about how to bleed out the air. any advise would be greatly appreciated.

 

[thunderroad]

Re: '69 mercruiser hydraulic hose replacement

My book said 10w30 or 10w40. There IS a process involved in getting the air out correctly. Some of the more experienced here might know a short-cut but I did it like what is printed in my service manual. A helper is handy to have too. On the "butt" end of the cylinder where the hoses connect, the hoses to the front are the "up" hoses and the ones to back are the "down". Disconnect all the hoses at the cylinders. Disconnect the rod end of the cylinders from the anchor pin. Fill the resevoir with oil. Run the pump in the "up" position until just a solid stream of oil comes out of the hoses. Then run the pump in the "down" position until the same thing happens. Now push in the cylinder rods by hand. Reconnect the "up" hoses. Lay a rag over the open "down" holes to keep oil from shooting everywhere in the next step. Fill the resevoir and run the pump in the "up" mode until the cylinders are fully extended. Now disconnect the "up" hoses again. Reconnect the "down" hoses, fill the resevoir, and run the pump in the "down" position until the rods are fully retracted. Now run the pump in the "up" position (the hoses are still disconnected, right?) until a solid stream of oil comes out of them. Reconnect the "up" hoses, check the oil level and cycle it a few times and you should be good to go. Don't ever let the resevoir go dry or you'll introduce more air into the system and you'll then have to start the process over.

 

[thunderroad]

Re: '69 mercruiser hydraulic hose replacement

On second thought...this whole procedure might be a little overkill for just replacing one hose. You might get by with just replacing the hose, filling the resevoir and cycling it a few times. On mine, one of the cylinder barrells was split so I had to completely disassemble the cylinder and change it out. I had gobs of air in my system after that.<br />This procedure worked great but I'll defer to the more experienced in the matter.