Here are 5 reasons I can think of off the top of my head (not in any particular order):
1. Most individuals purchasing a boat want either a cheap project boat (low cost, least work possible) or a sail-away (higher cost, but no work). Best guess is this project boat will be high cost and tons of work.
2. Very few potential buyers will have the technical know how and skills to carry it through properly and safely.
3. All parts depreciate significantly the instant one takes them out of the box, again with ownership transfer (lost warranties) and then the depreciation rate tails off with time, based on the ALE (Average Life Expectancy).
4. While every individual part may actually last longer or shorter than ALE, depreciation is typically based on the average. Any life beyond that is borrowed time, and expensive repair or replacement may well be required soon.
Hull - 30 years
Diesel Motor - 25 years
Electrical Wiring - 15 years
Electric Motor - 10 years (in salt water environment)
Electronics - 10 years
Sails - 20 years (cruiser), 10 years (avid sailor) 5 years (active PHRF club racer), 2 years (interclub trophy winner).
5. High risk - There is no guarantee the design will ever work satisfactorily.
Hope this helps.
1. I can see that.
2. This is certainly true. I could count the number of electric boat enthusiasts I've met in the Annapolis area on one hand, and most of those were selling things.
3. Sure. Same with pretty much any personally-owned transportation devices, from a scooter to a Rolls Royce. With certain cars, the curve eventually starts moving up again, but that's pretty rare. I've never seen a boat that appreciates. It's one of the things that makes them a good tax deduction.
4. Those are some seriously conservative lifetime expectations. Sounds like they were cooked up by West Marine to sell parts. Seriously though, unless you abuse your equipment, they should all last considerably longer than that. Except the sails - they are definitely on a flat use to wear curve. 40 year old motors and hulls aren't uncommon, provided they are maintained properly.
5. 'satisfactorily' is entirely subjective. I appreciate the guy's initiative and willingness to try, though. Maybe, like me, he's aiming for a design where he can replace the batteries down the road when the technology improves. A 50kWh pack won't get him too far, but a 500kWh pack certainly would. Who knows where we'll be in 5, 10, 20 years?