The problem with large cruising boats is the sample size is too small and the outfitting and condition.
Ford sells around a million F150s new each year and average lifespan is somewhere around 20yrs...so you likely have something on the order of 5-10million used sales each year. They can dial in the depreciation pretty well but even there, it's not unusual to see sales that are 20-30% off from the predicted value.
Now take a high production cruising boat. It might sell 100 per year...you simply aren't going to get the same kind of statistical
reliability out of depreciation estimates.
That said, my experience:
- First few years it's painful with large drops.
- Then out to maybe 15yrs, there are smaller but steady drops.
- By the time you get out to 20yrs, it's the condition and functional value of the boat with age having minimal impact (ie: a well maintained 50yr old boat will sell for more than a poorly maintained 25yr old boat).
It's a quirk of inflation but very common to see 20-30yr old boats selling for original sticker price...but once you discount for inflation, they still
lost a lot.