Mats, thank you for the resource and thank you both for your sound counsel.
Believe me, I've long thought about trashing my Saildrive and getting an outboard, maybe even a nice, quiet 4 stroke. But the Saildrive has been kind to me for the six years I've owned my O'Day, noisy and stinky, but it always started and always ran. Nevertheless, every year I start having anxiety dreams the month before we splash in May, and worry wonder whether it'll survive the 40 mile trip down to my harbor in Chicago if we can't raise the sails. During the season, I use it only to get in and out of the harbor.
When I started calling boat mechanics, I could hear the laughter when I told them what kind of engine I had just before they told me to never call again and slammed down the phone. I finally found a great mechanic who sails out of our harbor, and he diagnosed the problem right away.
It looks like in the midst of my panic I might have found a brand new starter, on Amazon, no less, for $97 and $3.99 overnight shipping. (Amazon fronts for Sierra Marine for boat parts, and usually prices its goods pretty reasonably.) Crowley Marine also looks to be a good source for old OMC parts. It looks like the starter is easy to install -- two bolts and a single wire connection. It should arrive tomorrow. Here's hoping.
But the next big thing that goes wrong will have me shopping for outboards again. It looks like there are plenty of gently used 9.9 hp long shaft motors on Craigslist, so I'm keeping my eye out. If I do have to go the outboard route, how much of a job is it removing the upper unit from the cramped bilges of the O'Day and glassing over the hole where the lower unit comes through the hull? The upper unit alone must weigh some 300 pounds, so I see no easy way to pull it out. I know I could just leave it in, but it would bug me carrying around that dead weight and the drag of the lower unit. Anybody ever do this job? In all events, I'll have to wait until we pull her out in the fall to consider doing it.
Good winds, all.