It seems every two years I need to replace shaft seals on my 6's. And if it not a seal it is a shaft that has a grove starting to cut the shaft. Is this common #6 problems or ?

I think the problem with the SSM drives, is they get water trapped in and behind the props. I dont know exactly why you are having these problems, but if in salt, i would remove the props after each boat ride, hose off the drives and propshafts, and let things dry out.

I have not tried that an yes it is salt. So you think better maintenance might be the answer? Once the props are on for the summer I usually don't take them off

FWIW I have an idea if it will fit. I don't have a #6 drive handy at the moment but I'll check on an old #3 in the morning.
There is a small flush mount press fit Monel stainless steel zerk or 'ball oiler' that is made. Part # MB1877M -1/8" Midget Oiler- Monel steel-Drive in fit- 11/64" depth-1/8" drill diameter-.123"-.125" fit. These specialty fittings are supplied by http://mbfittings.com/flush.htm
This just may be able to be carefully installed in the gear case in between the seals on the aluminum flat just above the propshaft. Once installed a few simple squirts of oil or light grease could be used to flush any contaminants out from between the two seals on the propshaft. Especially any water.
I got the idea while performing maintenance on my lathe today and squirting lubricant into the ball lubricators .This is just a thought, any ideas or suggestions?
Warren