I bet the answer is that you aren't going to spend $1M on anything. You intend to put the $1M in some very safe investment and live off the interest, correct?
So you don't really need $1M, what you need is $100K per year passive income. It's the same thing.
If you look at your problem that way, things seem more doable. Instead of spending 10 years making $1M, you can spend the same 10 years growing your passive income from $1K to $10K to $100K.
As somebody who has made a lot of money in real estate and in stocks ... and who has also lost much of it, I believe a business is a better investment for you than stocks or real estate. A business is a machine that produces money. Making your money in stocks or real estate is like hunting. Every time you go hunting, you may be lucky, but you may be unlucky. It's not conducive to a stress free state of mind.
Since your current business can't ever be passive, you'll need to start a new one that can be. Your sailboat electronics passion seems like a good one. Electronic products can be passive income and sailboat owners have money.
Good luck.