Can I replace the O Rings ??
Any precautions, or Tricks I should know ??
Or, should I take it to an Expert
Thanks, Larry

You can rebuild them yourself.It's not that hard.First you have to determine if you have internal lines or external.On the internal both of your lines screw into the cylinder next to each other.On the external, one line screws in on the end closest to the transom and the other line runs up the side of the cylinder and screws in to the cylinder near the ram end.There are o-ring kits for these,Internal kit is 25-47389A2(Internal is most popular)External is 86611A1.These can be found at ishopboating.com.Go to their website and click on Mercruiser Diagrams.Go down to Find Your Model.Under What Mercruiser product type select Sterndrive.Next question is What Catagory does it fit in,select TRS Drives.Then hit Show Models.On next screen go to TR/TRS 1977-1993.Hit search again.Scroll down to Trim Cylinder Repair Kits Internal or External.I've done business with this company and would recommend them to anyone.Very quick service.These cylinders can be seen in the Mercruiser Service Manual #5.If you don't have that manual there is a site called iboats boating forums.It's set up just like OSO. It's free to join and at the top they have Adults only.In there they have all the Mercruiser Manuals.Just go down to #9 Mercruiser Service Manuals,then select manual #5.This is for TR/TRS drives.As far as disassembling these you put the end that the lines screw into in a vise and then unscrew the large cap where the ram comes out with a pipe wrench.Keep all your parts in order as you take them out.It shows all the parts and order in the manual if you get stuck.

they are not that hard to do, just be carefull not to strip or cross thread lines into the housing. I had to replace one and it was about 230.00 for the bare (no guts) housing, ouch. I also had time in tracking down a spanner wrench to unscrew cap, other than that pretty easy.

Last year when I did mine, I got really lucky on the spanner wrench. I was able to make the one for my 5" angle grinder work!

Mercury manual shows using a large pipe wrench on the end caps.That's what I used and it worked fine.

I've done several sets. All were threaded on the end with a knurled fiting that could be unscrewed with a pipe wrench. They're very easy to rebuild. But as pointed out, be carefull with the hydraulic fittings, it's very easy to strip them out.

If you were to strip one out you can fix them easily.All you need is a small brass fitting which has male pipe threads on one side and female flare that fits your hyd.line on the other.3/16" is the flair size.
You have to get it at an auto parts store to get the correct flair thread size.Then all you do is drill it out and tap with correct pipe tap.Of course you would want to disassemble the cylinder first and flush well when finished.Less than 10 bucks!