Rebuilding Trim and Tilt Cylinders

Since I had everything else off for rebuilding, I decided to rebuild my trim/tilt cylinders as well.  They tended to leak down when they were hot, so I figured they needed new seals. The kit cost $25, one for each cylinder.  I ordered them from my local Bombardier/OMC dealer.  

The first step is to relieve the pressure in the trim system.  I ran the tilt all the way up (or to the point where the rods are fully extended).  I have a Cobra drive, so I have a relief valve on the side of the trim pump.  I turned that all the way out until it caught on the C-clip.

Once that's done, I carefully removed both trim lines from each cylinder and let them drain into a pan.  They drained for a while.  After that was done, I removed the cylinders from the gimbal housing by removing the nut from one side of the pivot shaft and pulled the shaft out.

Once both cylinders were free, I emptied them into a pan by running the piston in and out a few times.  Messy stuff.

Next, I used a spanner wrench and removed the service cap from the end of the cylinder and pulled the whole piston and rod assembly out of the cylinder.  I popped the plastic limiter off the shaft and set it aside.

The next step is the hardest - removing the cap on the shaft.  The only advice I can give you is to plan on heating the cap with a propane torch.  It loosens the thread locker used to hold it on, and makes removal much easier.  The soft-jaws I bought for my vice worked OK for this, but they were still a pain.  It took two people and lots of swearing to get them off, but they do come off.

Once the cap was off I pulled the service cap off the end and replaced the outside o-ring, inner o-ring and the scraper gasket.  That part was really easy.

Next, I removed the two split bearings and single o-ring from the piston and replaced those with new ones from the kit.  Be careful how the split bearings are placed - they can't overlap too much or be crooked when they go back into the bore.  Another note - make sure the split bearings have the split located in different areas of the piston once they're re-installed.  This helps to make sure wear is even and there's no direct path for oil to escape.

Next I snapped the limiter back onto the cylinder, oiled the service cap o-ring and seal and slid it back onto the shaft, stuck the assembly in a vice with soft-jaws and re-installed the cap after coating the shaft threads with lots of thread locker.  I used a wrench on the opposite side of the shaft (where the piston cushion sits) for leverage.

Once that was finished, I cut up a pop can as a guide for the piston and it's split bearings (they like to pop off if they're not being held in place).  I stuck the pop can/piston guide into the cylinder bore, oiled it all up, and slid the piston assembly (with limiter snapped on the shaft - don't forget! Guess how I know...) into the bore.  I made sure before giving it a bump to get everything in there that the bearings and o-ring hadn't moved out of position.

Once that was done, I used the spanner wrench to re-install the service cap, and then re-installed the trim cylinders!  In all, it took less than 2 hours to do both.  A very easy job.

On to the next step: Buffing Fiberglass