I just ordered the new Pertronix Billet Marine distributor. They just came out with it, and I should have it in a week. It comes with the Ignitor II module, cap and rotor. They also supply 3 sets of advance springs, and adjustable advance stops to limit total advance. Looks like a nice part, and at a nice price ($189.00 through carshopinc.com). I'll update when I get it.
(Can't wait)

most marine distributors do not have mechanical advance. check it out.

I know they don't have vacuum advance (which this one doesn't), but mechanical??? Every marine distributor Ive ever seen has mechanical advance. Granted, some people lock it out, but it still has it.

The T bolts and aftermarkets that use a module to for advance do not have a mechanical (springs/weights) advance. Points types, HEI, and the pertronix do use a mechanical advance. Dont worry about it. Just be sure it's a USCG rated marine distributor.
Just curious, did you swap out a points distributoror a Merc T bolt?

Gary,
I have a 1988 OMC setup (Last year they used points on V8), so this is a new electronic conversion for me. I went with the Pertronix because I know people who have used their modules with good results, and the great price! I built their little shift assist fix circuit, and potted it. As you said, Pertronix modules don't use programmed advance. It's all done with weights and springs which I prefer for this application. The module does however use adaptive dwell control which I won't explain to you, because I'm sure you know what that is. I spoke with one of the engineers at Pertronix, and the told me the distributor is USCG approved. We'll see how it works. I'll keep my old one in the tool box just in case.

Did the exact same thing with my old 1988 OMC (including the potting of the ESM bypass) only with a Mallory and it was great.