50HP Johnson Slowly dropping in water

Hey guys, just recently bought a (new to me) boat. The power trim unit was leaking out the top of the cylinder around the ram wiper seal. Bought the $70 O-ring kit, took it apart and replaced all the seals and O-rings in the cylinder. Did not replace or touch anything in the other side. I did as well replace the motor on the unit. The cylinder on the inside looked clean and free of any scoring or anything. Put it back together and added fluid till it starting going up and down. Well ive taken it in the water twice since and noticed when I trim my motor to get my max RPMs, the motor slowly trims back down on its own. I basically have to keep trimming up every few seconds to stay at my max RPMs when running WOT. Is it a possibility that I haven't put enough fluid back in the system? I do hear a little "bubbling" when I trim up so I'm assuming there is still air in there even though it should be self bled. How do I know when my system is full? thanks in advance!

Raise the mtr to the full tilt position then top off the fluid. Cycle the mtr up and down 10 times checking the fluid level while doing this. Then see what happens.

10-4 I'll give it a try this weekend when I get it back in the water. It doesn't do it while on the trailer, only in the water so it almost seems like the thrust of the prop when in gear is pushing it all the way down while I'm driving.

Update: I finally got some more power trim fluid from Walmart, squeezed some more in yesturday till it was coming back out so I'm assuming it's full, put the boat in the water and it still does the same thing. Slowly dropping the trim all the way down while running. I'm assuming now it's a seal inside? I just rebuilt the ram. The check balls and Springs looked fine. What am I missing?

Did you follow my directions in post #2 ??

I did lift the motor all the way up when I added the fluid. I went up and down a couple times, unscrewed the cap (fluid started coming out), squeezed more in there, put the motor up and down again a couple of times, repeated process. Every time I unscrewed the full screw fluid started coming out so I took that as its full. Put it in the water and it did the same thing. I can try trimming up and down some more to bleed any air but I don't know. I guess I could try parking it on a hill to try and get more fluid in??

Saw a video of a guy who was having the same problems and his culprit was a bad o ring on his relief valve. I took mine out today and I did have a few knicks in one and I had some black looking o ring debris come out. I replaced the o rings and got the junk out and put it back in, raised and lowered it numerous times and added fluid till it was full but the thing is still lowering slowly on its own. I have no clue..

Got a model # ??

The boat sticker that had all that info is unreadable since I bought the boat. From doing online research I'm pretty sure it's a J50PLSSA I think. It's a 2000 johnson 50hp with electric start, remote steering, power trim obviously. Thanks for sticking with me on this.

I haven't got one but if you could find a factory service manual on tilt unit they have good trouble shooting info and diagrams in it.

One more thing I just thought of, It could be a bad manual relief valve. Good Night !!

I agree is the manual release valve tight? Could be a leaking o-ring?

I'll look into a manual. Didn't know they had trouble shooting too in them. Thanks Bobbie. Kimcrwbr1 I will check again but it has new o rings and is tight. Thanks

Well, what happened ??

Haven't got a manual yet. I did open the manual relief valve and trim it up and down to try and bleed air, checked the fluid level at the fill port trimmed up and down and it was full I assume since fluid started coming out as soon as I loosened it. I'm dreading it but I'm thinking I'm going to have to pull it apart again. Is it possible that the poppet springs are just weak allowing fluid to flow backwards when trimmed up? After trimming up I do hear a faint popping sound coming from the unit, almost like how your car dash sounds when it's hot out and you get in and turn the AC on. That plastic popping sound. I forgot to mention when it leaks, it's not fast. Probably 1/4 inch every 5 min.

ok lets start again.

if boat is on a trailer, then lower the font of the trailer as far down as possible.
lets begin bleeding this monster

1/ fist of all make sure the relief valve is fully closed !!!!
2/ trim it all the way up and chock the motor, unscrew oil cap and slowly very slowly fill it to the top. put cap back on tight...
3/ fully lower and fully raise atleast 5 times then raise fully up to the top chock motor, wait 1 minute then lowly open the cap, you might even hear it hissing when
opening the cap.
4/ now top It up again and tighten oil cap....lower a raise it now about 10 times and check the fluid again like above.
5/ once you thin its all ok double check to see if any oil is leaking anywhere on the trim system.
6/ even if its now perfect and trouble free , report back to let us know results.

10-4. Give me a couple days. I actually have a hill next to my house so I'll park it on the hill, bow facing down to give me a max angle when filling. I need to find a tube as well. I've just been using the squeeze tube and trying to squeeze it in and then cap it quickly before it all comes back out. It does hiss when after trimming when I pull the fill screw off. Will get back soon with results. Thanks guys for bearing with me.

Alright phillnjack, I did everything you said. Only thing is every time I opened the fill cap, fluid would come running out to I had to refill a little everytime so I probably didn't gain any fluid, the trailer was all the way down on a hill with the back jacked up a little so I think it's full. It did have some pressure behind it each time. No leaks though. After doing the hole process, I measured an area, waited and measured again. It still dropped 3/16" in 8 minutes. Not as bad as before but still dropping. Which I'm sure it will do the same in the water as well. I'm trying to get it fixed before my first beach trip with the boat in 2 weeks. Any other tricks or tips? When I had it all open the whole inside looked great. The piston even gave significant resistance when I put it back in the cylinder when reassembling it so the seals and all should be good. Springs and check balls looked fine. I did however notice that out of the 5 or 6 check ball ports I have in the ram, one of them didn't have a check ball, it had a plastic orange flat headed piece with the spring. Not sure what that is for. I assume it's serves the same purpose as the balls but I don't see how it can get the same seal since it is flat on top versus round. I don't know. ??

I think you need to replace the seals that you have not touched.
did you replace any of the seals/ o-rings on the relief side ?

Only on the relief valve itself. When I replaced the motor I looked down in there where the filter and all is but I didn't see any immediate seals and didn't want to touch anything so I left that side alone.