Value of engines?

[Frencl]

Greetings all,

I have a '75 233 with twin 1999 volvo penta 3.0gs with sx cobra outdrives.  I've been pondering on snatching these out and putting outboards on the back.  If I did this I would obviously want to sell the volvo pentas, but I can't seem to find anything on what the value of these things are.

Does anyone have any insight on what the value may be?  Thanks in advance