the pressure dropping to 0 psi on a TBI system after shutdown is normal. there's actually a bleed off orifice in the regulator. this is not like "modern" EFI.

https://marine-performance-parts.com...843505774.aspx

If your pressure is indeed 17psi, it is too high for a stock engine, i usually shoot for 13-14psi on stock stuff myself. you can make the stock regulator adjustable.