Go with him to get the cashiers checks, then it's as good as cash. Rule #1
Then, for the off off off chance he wants to complicate things later, the only possibly way he can get his money back is if he initiates a 90 day+ process where he has to show that he didn't get what he paid for and...
Used mine twice and then on the third use it swelled up and I got scared and threw it in the water lol.
If you have a small car it's pretty slick but I'd just keep a full sized one in the boat or truck.
Probably this. I've experienced the opposite too on my old boat and current boat. Probably related to angle of trim. Also, perhaps when the boat is running there is some leaking coolant water from a hose? I heard the gimbal bearing can leak too.