Look for an engine of about 95hp. All engines are good but there is a bit of a range on the quality of conversions and they are all conversions. Join Boatdiesel.com and read about the engines and the comments on the forums by experts and others. I joined BD a few months ago and have'nt been there much but I'm already re-powered. Klassen Engines may have something for you**** ....the're made in Canada. Ther'es a Fisher on yachtworld with your displacement that has a new 85hp Deere. The Nordhavn 46 came w a 101hp Lugger. Look at all the boats like yours (mostly regarding displacement) that you can find regarding disp and compare. If you have lots of head on windage such as a motor sailer another 10 or 15 hp may be better. If your hull is more efficient than a Krogen 42 or a Nordhavn 46 75hp may be all that you need. In my opinion engine speed should not be an issue but use the calculators on BD to see what reduction ratio you will require to swing the propeller that is best for your boat. If you chose an engine much lighter than the original consider CG and ballest. Again** ..go to Boatdiesel. You'll be lucky if Larry M responds here.