Re: 98 force 120 starter issues
The fast clicking noise is the solinoid trying to work but it doesn't have enough power.
The first thing to do is verify the battery is good. If you don't have a high rate discharge tester, then take it to Walmart or Pep Boys and ask them to check it for you.
Once you know you have a good battery, then you need to clean all of the terminals on the wires going to the battery until they shine. Also, check the attachments at the engine and make sure that the red wires on the solinoid and black wire on the block are not corroded. If they are, clean them until they shine, including the area on the block where the terminal end is bolted.
If this doesn't fix it, then you may have a bad solinoid. Solinoids don't go bad that often on boats as they don't get the start cycles like cars get.
I am willing to bet it is a bad battery or corroded terminals.
Keep us up on what you find.
John