Re: How old is your boat and how often does it break down ?
If I had been really stranded, I wouldn't be here typing. But I have been temporarily detained.
Anyone who says a motor won't break down if it's well maintained is both insufferably self-righteous, and wrong. It is true, however, that a well-maintained motor (and related systems) is less likely to fail than a poorly maintained one--that is a no brainer. Many new boaters do not understand that boats need a different level of care than their cars, especially in salt water. And with the ethanol issue, babying the fuel is essential--all the mechanics will tell you that the vast majority of their work today is fuel related.
Right now my 1972 Merc 20 hp won't start, so it won't leave me stranded. On the list to fix. Point is--do you count as "stranded" times when you can't use the boat due to mechanical issues encountered before you leave the dock?
My 1987 Johnson 70 intermittently blows a 20A fuse. Been chasing it for months. I think I have it fixed--new wiring harness. Until then, I carry fuses.
It replaced a 1988 that died from salt water in the gas from the vent---that stranded my BIL but I towed him with another boat. Several years previous it ran without oil (VRO system) and seized; rebuilt it. That one (I'll admit probably due to carelessness, being in a hurry, making assumptions, etc.) stranded my daughter, but I was nearby in another boat. Moral: have an extra boat when you are in remote areas! (buddy system)
Found the steering locked up on launch and had to beat a falling tide; disconnected the arm and tied a paddle to the motor for a tiller. In my old whaler as a boy I busted a bucket full of shear pins, and I wrapped a crab trap around the prop in the dark going duck hunting--these are not strandings, just part of boating.
I have towed a lot of people in my day.
Old boats, hard use, high salt conditions--stuff will happen no matter who you are. You may not know that your heat/oil alarms aren't working, so you never count on them. I carry tools and am very resourceful--that's why I'm here to tell you about it.