Glad to hear it was an easy fix! It's weird how quickly they go bad. Before I had work on my boat for a year and didn't use, except when the dealership ran it on occasion for a total of 2-3 hours for the entire year, I had just down all the maintenance, including the spark plugs. When I got my boat back and took it out, one engine sounded funny, kinda like a lawn mower, and vibrating more than the other. When the dashboard told me low oil pressure, new spark plugs fixed all of those problems.
In my opinion, I think spark plugs go bad a lot quicker if the boat isn't used much. I generally use mine quite a bit like I put maybe 100hrs a year, but never had spark plugs go bad in the year I used them. But when it was at the shop for so long it did. I have a neighbor with a SeaDoo who doesn't take his out as often (put 65hrs in 10yrs) and he always tells me how he always has issues with his spark plugs and gave me the advice to keep a spare pack onboard, along with other emergency repair tools. Probably not helpful now, but something to think about.