mine floated
 

When I was buying my '89 SF20 last year, I ask my mechanic to test drive it, without me. he only had put the plugs in the stern, and forgot to put in the fishbox plug. He had a marina fork lift put it in, he ran it out the channel for about 20 mins. brought it back and had them lift it out. said it rode like a heavy boat but didn't think much of it.

once back on the cradle, I showed up and noticed the plugs still in, so I pulled one and it pissed a full stream of water for 15 to 20 minutes. it is amazing it didn't sink.