I'm guessing that he read something wrong or somebody gave him some inaccurate information.
Kawasaki sells their engines through Kawasaki authorized dealers. Any Kawasaki dealer should be able to supply the 17 hp we use. Send me an e-mail to firstname.lastname@example.org with your serial number and I'll give you the "spec" number for the 17 hp used on your machine.
I'm sure he's being given this information by somebody but it's not accurate. Send me a pm to email@example.com with your the name of your dealer, his phone number and who you've been talking to. I'll give them a call and try to straighten things out or at least get them with someone at Kawasaki that can straighten things out. Also let me know why your are swapping out a perfectly good engine?
ALL engines on all models used on any Exmark equipment ever built can be purchased through any dealer authorized by the engine manufacturer.