Captive nuts.

[BurnitBlue]

Might I also suggest you plug the existing holes and once you are satisfied with the location of the engine use the lag screws i suggested. This is exactly what I did when I changed engines where the mounts were in slightly different locations - one set overlapping the old ones. Used M10*50mm. Remember now the pilot holes were 10mm for the first part where the screw is unthreaded and 8mm for the screw part. Much simpler than trying to insert threaded plates. As a permanent fix you won't then need the spacer as you set up the shaft exactly where you want it and then drill.

When replacing engines the only fixed datum point is the flange on the shaft and you fit the engine to that, making any changes necessary to the beds.

I will take a dozen lag screws with me to Greece in case the original bearers are wide enough to take them. The Yanmar is a narrow engine compared to the Thornycroft 90 that was installed. So the width of the engine bearers may not be wide enough to allow lag screws if they will be close to the edge. I am reluctant to mess with the bearers because they are dimensioned for the sump of a four cylinder beast. Next owner may object. The engine has been bolted temporarily for the last two years to a thick shim waiting for me to locate captive nuts. All great suggestions, I wish I had asked two years ago instead of thinking captive nuts were the only answer. Greece is great when buying tomatoes and oranges in season. Sweden is actually not much better when looking for something more complex than a meatball. I have to order most things from UK.