We were just discussing boat liability the other day. Long story short, you will likely be liable when the boat is borrowed. Buy insurance.
I just left our lake house, where 2 families have been sharing 3 boats for the past 20 years (really long story). We know that the owner is the one liable for what the guests do, and accept that risk.
The first thing I worry about when it comes to a boat is huge costs of maintenance and them breaking randomly.... as far as liability, just make sure you have insurance on the boat and the standard umbrella which you should have anyway.
This. We would never loan out our boat to anyone - they could come out with us and that was the option. If others felt they could go out on their own - let them rent a boat at a rental company. We finally sold our boat - it's true when they say BOAT stands for "Break Out Another Thousand". Now we have kayaks - and extra for people to come with. A lot less on the maintenance costs and we can rent a boat sometime if we really want to go out deep.
Buy the insurance, no second thoughts should be had.
Also remember that boats are giant money pits. We have one and all it does is cost money. However, we knew this going in and plan accordingly. Also, I wouldn't lend out my boat to anyone. Boats are 1) hard to drive, 2) easy to crash, and 3) most people have no clue what the actual rules of the water are. Also, whomever you lend to needs to know the topography of the water to ensure that they do not go into too shallow of water.
One other thing - make sure you know the boating requirement for anyone you think of lending to. In some states, any driver needs a boater education card. I'd absolutely not lend it to anyone without it if it's needed in your state.
I guess this is a hard one since you rent out your house. I was going to tell you "just tell them they can't use the boat" but I can see how the line gets fuzzy since they use your other stuff already.
At the end of the day though it is your property and if you wouldn't loan them something like your car, there is no reason they should expect to use your boat either. Are you concerned mostly because it is coming from their parents so they will think they have rights to it? If so, I'd pass on this boat and just buy another later that they won't have that connection to.
Why are boat maintenance costs so high? DH has been talking a lot about buying a boat in the last couple of years. We're not financially ready for that right now but I can see it being a possibility in the next 3-5 years (maybe even slightly sooner?). I'm scared that I don't know enough and will be caught off guard with random costs!
Is this boat 'more boat' than you were otherwise planning to buy in a few years, if that makes sense? If so, I'd pass and just buy something more practical for your family when the timing is better.
If it is the type of boat you plan to buy and it's at such a fantastic price and you know the good history of it, I'd go ahead and buy it. Absolutely I'd say no to anyone asking to borrow (well I have a hard time saying no so I'd make DH so no) and definitely off limits to renters. Just tell people your insurance over covers you and DH as drivers-no one else (probably not true but they won't know that; permissive drivers are covered just like cars). Yes, as the owner you'd be liable--your insurance would be primary.
I'd suggest getting an umbrella policy in addition to your primary insurance. They run about $200 bucks for $1 million in coverage and would provide extra protection God forbid something were to happen.
In the event of a catastrophic accident, both the owner and operator are liable if you are letting someone borrow it (at least in Georgia you can get sued as the operator of a borrowed watercraft). I say get the boat if it's a good deal and since you already have a lake house and a place to store it, but I wouldn't let anyone borrow it, not even siblings. Too much risk for me.
Even if you don't get it, its highly recommended that everyone get an umbrella insurance policy. It covers so much re:liability & its really cheap...like $150 a year for $1m worth of coverage.
DH & FIL own a boat together. We don't let anyone else borrow it. If they want to come along that is fine. It can get pricey but so far any fix has been pretty minimal.