Shamp,
I had a 150 Eninrude that I had to change these seals a couple of times. If is not dificult at all unless there is heavy corrosion on the threads of the cap. There is nothing in there that will pop out at you, well maybee some hydrolic oil.
Here we go:
The parts that need changing are the outer scrapper ring that cleans the piston as it retracts and keeps water out, an inner o-ring or quad ring seal that keeps oil in, and a nylon washer that is at the bottom of the cap.
The tool to remove the cap cost about $60 last time I priced it a couple of years ago or you can make your own.
To make your own tool get a thick washer that the same diameter of the cap. Find 2 or 4 bolts depending on if the cap has 2 or 4 holes in it. The bolts should be about 3 inches long and should fit snuggly in the cap holes. Now drill and tap 2 or 4 holes in the washer in the same location as the holes in the cap. Screw the bolts into the washer and and place this contraption onto the cap inserting the bolts into the holes of the cap. Now Use a channel lock or pipe wrench to unscrew the cap counter clock wise. Once the cap is loose keep unscrewing it untill you can take it off, there are quite a few threads on it. Once the cap is off use a small screw driver to remove the worn o-rings and and replace with new ones. If the cap is corroded you should replace that too. Install the cap by screwing it down and tighten snuggly.
This worked great for me. If you have any questions let me know.
Pete
