Just to be clear: is the port tilt and trim leaking to allow the engine to go from all of the way up at trailering position, and then dropping down, which pulls the steering cylinder "out", and when you raise it up, then the engines. are out of alignment? The "ideal" trim of the catamaran engines, is slight toe in. About 1/2" is generally good for the 255. However best to "align" by leaving the port engine free (open liquid tie bar) and let it self align at planing speed. Then close the equalizing valve.
I always leave my engines down. Even in a slip--then I put a trashbag, with fresh water in it as a "jacket" around the lower unit of the outboard. Another option is a "Boat bath" which is a fairly thick plastic lets say at least 8 mills. It is supported by the floating docks, and moves up and down with the tide. The exception might be when I am fishing every day, as we did in the keys. Then I use the hose to wrinse out the engine blocks and leave the motors as in running position.
I don't have a photo, but my recollection is that there is a nitral "O" ring which fits over the disc which is fixed to the center of the shaft. Nothing fancy. You are going to have to remove the piston shaft to varify the size. However, I suggest that you contact "Dometic Marine" who currently owns Sea Star. Their chief engineer is very helpful.
Here is the contact info.
Dometic Marine Global Tech Support
marinesupport@dometic.com
800-730-4082 Menu has changed.
1. DG3 Gyro
2. Optimus
3. Hydraulics
4. AC, Marine Climate
5. Balmar
6. Oceanair Blinds
7. Digital Switching & MDI
9. RV/Land Services
0. All others including Mechanical Steering & Controls, Sierra engine parts, Shields hoses
Moeller Fuel tanks, portable coolers, and more.