On the day that the (possibly) perfect solution for the engine pops up on this site, our offer got turned down. The owner says it doesn't need a new engine, the current one can easily be fixed. I wonder if he ever took a look under the sundeck...
He said we should check it out together with a mechanic and then negotiate. I don't think we'll come to a deal as it seems he's thinking he has a perfect boat there, but we'll give it a shot.
Hope that engine is still around if/when we can make a deal.
Either way, thanks for all the support everybody!