Download the manual for your model year. You can find a lot of specifications there or use google:
site:
www.greatgrady.com “search term”
That search term has saved me a lot of time and helped me get answers faster than even replies from from fellow forum members.
Download a free copy of your Grady-White owners' manual.
www.gradywhite.com
The old manuals aren’t as detailed as the new but they specify 800 or 1100 gpm. Check your fuse size to verify what you have. Also check wiring condition since the boat is 32 years old...