Trim pump problem

[soulsalvation]

I believe there may be an O ring issue in the trim pump valve assembly as my stern drive doesn’t stay up for long and drops overnight. I can manually lift the drive about halfway and then it stops. I ruled out air in the line as I did a complete bleed last year before storage. The motor works fine to raise and lower but it doesn’t stay where positionEd.
My engine is a 1975 Ford Mercruiser 233hp 351cu and the stern drive is probably an Alpha series pre Bravo . I cannot find the engine’s serial number. I’m also considering replacing the whole system but need to find the right system compatible to that engine/stern drive year. Anyone out there that has a similar setup who can poin me in the right direction would be greatly appreciated. The existing pump I have is in the photos that I’ve uploaded. Thanks to all who respond.

 

[achris]

Could be the valves in the pump, could also be one (or both) hydraulic cylinders are bypassing.

Before replacing the pump (expensive) I'd put a kit through each cylinder (cheap)...

Chris....

 

[kenny nunez]

Check under the pump where the 4 bolts hold the valve body to see if any are loose and if there is fluid leaking from the bottom. If the body has to come off disconnect the lines and remove the bolts. There are 4 “O” rings under the valve body which can be matched up at any auto store. Quite often the body is warped from the high pressure. Put the body on a flat surface and you will see the distortion. A good flat file and various grades of sand paper will straighten it out. Use some grease to hold the “O” rings for re assembly. Easy and cheap fix.
As Chris said the rams are also cheap to reseal.
MCM # 25-87400A2 Ram seal kit
Sierra# 18-2649. Ram seal kit

 

[soulsalvation]

Check under the pump where the 4 bolts hold the valve body to see if any are loose and if there is fluid leaking from the bottom. If the body has to come off disconnect the lines and remove the bolts. There are 4 “O” rings under the valve body which can be matched up at any auto store. Quite often the body is warped from the high pressure. Put the body on a flat surface and you will see the distortion. A good flat file and various grades of sand paper will straighten it out. Use some grease to hold the “O” rings for re assembly. Easy and cheap fix.
As Chris said the rams are also cheap to reseal.
MCM # 25-87400A2 Ram seal kit
Sierra# 18-2649. Ram seal kit

Check under the pump where the 4 bolts hold the valve body to see if any are loose and if there is fluid leaking from the bottom. If the body has to come off disconnect the lines and remove the bolts. There are 4 “O” rings under the valve body which can be matched up at any auto store. Quite often the body is warped from the high pressure. Put the body on a flat surface and you will see the distortion. A good flat file and various grades of sand paper will straighten it out. Use some grease to hold the “O” rings for re assembly. Easy and cheap fix.
As Chris said the rams are also cheap to reseal.
MCM # 25-87400A2 Ram seal kit
Sierra# 18-2649. Ram seal kit

There are no leaks anywhere and I will see once again if air is the lines. Thanks for the information on seal kits. I will definitely look into that.