Like everyone says, be sure you have an actual gear lube leak, before going crazy ripping into the gearcase. Have you run the engine on a boat? I only ask because you mention that the gear lube is clean when you drain it….There should be evidence of water in the gear lube when you drain it after running it on a boat if there is a gear lube leak.
It is critical to pressure test the gearcase prior to ripping it apart and replacing all the seals/orings. You really want to know just what is causing the leak before ripping it apart. All the new seals/orings aren’t going to solve a leak issue caused by a damaged casting or grooved shaft.
I am in the minority here, I disagree with all that insist that doing a reseal job on one of these clam shell gearcases is something that can be successfully tackled by a novice without any prior experience or proper tools. These gearcases are in fact pretty difficult to get sealed up properly. Yes, most can probably get the thing apart and together with new seals/orings. but sealing it up successfully is quite another story.
So, I am inclined to discourage folks from taking these thing apart. Needless to say, I have no idea what your experience level is, or what tools you have access to. I would run the thing on a boat, and change the gear lube very frequently to monitor this issue. If you decide that the leak is severe and the gearcase must come apart, please pressure test it first prior to disassembly…Next, I would get a manual and review the procedures, ask questions here, and gather up the tools you will need prior to getting started…
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