Haha reminds me of when I had an old I/O I found a similar nest under the folding rear deck where the bimini was stored. The bimini was all torn up to make the nest but I never found him.
Then when I went out the following weekend we were under way when were heard a huge screech and the motor died-- I was certain the thing got scared and jumped up into the fan belts!
Turned out the lower unit had seized up but it was still great for some good laughs while we were stranded-- talking about how the rat had got what he deserved for tearing all our stuff up.