I have concerns about the economy the next few years as many others have mentioned. There’s also no doubt that many people have over extended their finances through endless payments (just look at the statistics on how many Americans can cover a $1000 emergency and you will see the bleak picture pretty quickly).
Related to boat/motorcycle/snowmobile market I think a key driver of the inflated used prices is the inflated new prices. I could sell the used snowmobile I bought 5 years ago for the same price today which is crazy because the value of a sled usually drops like a rock as you put miles on them. Using rough estimates, you could buy a new sled for $8-9K say 6 years ago. Now they are $14K. When prices inflate so quickly the used market tends to follow as a percentage of the new prices.