Center Console Boats And More

Why wont my boat start right away?

I have a 25HP Mercury motor on my 14ft fishing boat. When you first start it for the day it will take like 4-5 minutes to finally get it started. It will turn but not go over all the way.
After you get it started the first time, you hardly have to touch the key and it starts. Im pretty sure the battery is good.
What could it be?

Thanks for your time