I sail in similar water temps, and cooler air temps. I own breathing drysuits, spray suits built of non breathing fabric,wet suits, and lots of different kind of under-clothes.

I would not wear a drysuit in Air temps above 73ºF unless it was:
Extrememly windy
going to be a long day on the water
water temp was less than 60ºF
no visible sunshine (clouds reduce radiant heat)
no option of a spray suit or spray top and bottom

They're just too hot for warm weather on a casual outing.

If you wear a breathable drysuit in the warm conditions then you will likely have soaking wet underclothes at day's end. You can produce persperation faster than the suit can pass it.

GARY