Mercury classic 50 power trim

I have a 1988 Mercury classic 50, but the power trim very slowly bleeds down. It raises and lowers just fine, but it won't stay. It's on a Lund stinger and the pump is located in the hull. It really looks to be a pain to get to in order to remove the entire pump assembly, almost like lund installed the tilt pump, then built the rest of the boat. I've already changed the solenoids and they weren't too much of an issue, because they were located on top, but I can't even see where the reservoir is located in order to check the easiest fix (low hydraulic fluid). I'm mechanically inclined enough to do the work myself, but if the issue isn't fixable,and/or I can't get parts, I don't want to waste my time either. My questions are: 1) Is there a better way to get to the pump that I may be overlooking? 2) Assuming the answer to #1 is no and I have contort my arms through the top "access hole" and the small area on the sides where the batteries are located, laying on my side inside the boat to remove the pump, are there even parts available to fix the issue given the age of the motor and trim? 3) Are there any other options other than traiding in the boat for a new one? Any and all help is appreciated. Thanks

Your location ?-----Lots those units available in some areas.------Plug to fill is in one corner on top of the reservoir.-----Just takes #30 motor oil.

Illinois. Thanks for the info. I'll go try to find the plug again

@racerone... Pretty sure I found the fill plug. Thanks! I was looking for a bigger plug the whole time. This was just a phillips head screw. Looked like a #10 about an inch long on the corner. I took it out and stuck a nail down the hole and it struck oil. While I was looking for the plug, I also noticed a thumbscrew type valve toward the bottom of the same oil tank that was about half open (moved freely in both directions). I was hoping that by closing that valve, it would solve the issue, but it didn't. I even tried bottoming out the valve in both directions. Maybe faulty O ring on that valve? Thank you for your help!

I believe I have a tilt/trim system on my '85 - 60 hp Merc. The valve at the bottom of the tilt pump is a reverse lift lock. It allows you to manually tilt the motor up without power and keep the motor from popping up when applying power in reverse. I don't remember which end stop is which but it is easy to test. The CCW stop is one position and the CW stop is the other.

If you are not holding in position my guess is that you have a cylinder that is leaking by.

@FishinLite....That makes sense, because if it was the relief valve it should have sped the drop or slowed it down depending on which direction, but it had no affect in both CW and CCW stop positions. My unit has two cylinders on the outboard side of the transom. Is there a way of testing them one at a time for leaking by? I'm not sure if they both lift/lower the motor at the same time, or if one lifts and the other lowers. Thanks

I would say with 4 hoses that oil is supplied to the cylinders the same way for both sides.

Sounds like you have air or shortage of fluid.I'm going to hazard a guess this is what you've got.
With the motor full up, the fill screw and the vent screw,small screw above the fill screw, open and fill with fluid,operate the trim up and down,check the oil level and top up.Repeat until the level stay at the bottom of the fill hole screw threads.Oh and make sure it's the same oil/fluid as what's in there.
Make sure the knob is turned full CCW,or full CW to lift engine manually

@havenaclue… Thanks. I'll do that tonight after work. I really appreciate everyone's help!!

It was short on oil and I filled it, ran it up and down several times. That slowed the downward drift down significantly, but didn't stop it. So unless there is residual air still in the lines, which is possible, oil shortage isn't the fix for my issue. I checked for leaks, but didn't find any which doesn't make sense because the oil wouldn't have just evaporated. I'm going to look for new units, but have a dumb question. As long as the hose connections are the same size, I should be able to replace my unit with any comparable aftermarket unit right? (in case the correct part number isn't available). Most likely, I'll rebuild the cylinders first though as they are on the outside and easy to access. Thanks for the advise!

Took me almost an hour to fully bleed my system after installing in boat and I had system completely drained,hoses disconnected.These are a straight forward pump,plenty of O rings to replace on the rams,if you have the Seloc manual page 9-11 has the sizes required.Copyright laws prevent me from posting pic. https://www.ebay.ie/itm/Mercury-Mer...Relays-USED-/233627483944?hash=item3665487f28 For illustration purposes only,I have no connection nor do I know the seller,but this is what you need if replacing,but I think the rams may need a few O rings as well,but try running it up and down a couple more times,making sure the reverse lock screw is turned full anti cw/left

thanks!