Because this is offshore, it is best to remove your motor and measure the shaft - you are going to remove it anyway.
Took the motor off as soon as the bride and grandkids blew out of town. That's one heavy motor!!!
Turns out that the shaft has a 0.980 (w calipers square) shoulder. The shaft itself turned out to be 0.870 (21.98mm) over 2.024" with an OAL of 2.561 including the shoulder. The key is 0.269 x 0.275 and appeared to be ground on both of the wider sides.
The motor housing is mounted with a 9-5/16 (236.5mm) bolt spacing on special 7/16-20 [] 1/2-18 shouldered cam bolts for easy belt changes and adjustment. I gotta admit that these cam-bolts are pretty slick!
The pulley was a press fit to the shaft. I had to use a puller to get it off. To top that off, it was attached with two Allen Plugs with Blue Lock-Tite. Somebody must have been scared to death of having that pulley come off.
I can open the pulley enough to take a standard 0.875 shaft, but I confess that I am worried now about the other motor dimensions.
I tried looking up motor dimensions and ended up totally bewildered (AGAIN). Don't those motor people talk to each other? How the heck do I figure out what motor I need?