One of the things that can affect marine engines is salt. Has this one been run in the salt water?
If so, perhaps a few bolts broke, and other complications came with it.
If not, maybe it sat in mineral water.....
It sounds High to me, but 50 buks an hr is not too bad. Usually good shops are charging 75 an hr and some 100 buks an hr.
But, for a real good mechanic, they really can get alot done in an hr.
Let somebody else chime in. I like to let corroded bolts soak alot.
And, I suggest a flat price for future repairs. A really smart shop will sometimes say: We will fix it for a flat fee of______, unless we find other problems inside. After we take it apart, and see, we will call you and let you know if we find other issues....
Nate