Can I upgrade the logic board of my 2015 with a 2017 logicboard?

Oh Boy! Not good … At this point the cost of a new system would be cheaper! Apple has dropped the price so low it doesn’t really make sense fixing this series when you need a display, keyboard/trackpad or logic board, between the cost of the part and the labor. A true throw-away system - So sad …

I’ve not tried doing this so I don’t know if you’ll encounter any issues. Just looking at the system tear downs they do appear to be exactly the same shape and the connections look the same. So I would say your chanced are good if you can get a cheap board somehow.

Do keep in mind reselling your system won’t allow you to recover the cost.