Re: Big Twin Lower Unit Reseal Question

[Don]

These gearcases are a royal pain to seal properly. I think I am hearing you say that when you pressure test, no leaks are evident, is this correct? While pressure testing, are you rotating the shafts, and pulling the shift rod up and down? It is really helpful to submerge the gearcase completely in a trash can full of water while pressure testing to pinpoint the leak/area.
Like Ed says, these shafts are often grooved, but may not show leakage unless you rotate the shafts while pulling in/out on them.
Using a vacuum tester on single seal systems can cause confusion, because you don’t have the outer facing seal, and the vacuum tester might overcome the single seal. I don’t think you will be able to use two seals on these gearcases.
Try pressure testing again in a bucket of water while rotating/pulling the shafts and pulling up/down on the shift rod, I think the problem area will show up.