IIRC I paid about £4000 for my first share in 1992 and sold the share for £3750 in 2001, even though the boat needed a new engine. However in those days shared ownership was in great demand so the shares held their value very well.
The share in the second boat cost about £6500 new and I sold it for £3250 in 2013. It had just had a new engine fitted which cost each shareholder about £500 IIRC.
I then spent a long time looking for a suitable secondhand boat to buy, and eventually bought one in May 2014.
The first share multiplied by 12 was more than the boats value, the second probably reflected the boats value, but be aware secondhand boat prices have risen dramatically (an unusual situation) since 2013, although they are beginning to soften now. For example I had my boat valued earlier this year and it is worth around 45% more than the amount I paid for it in 2014.