It happens even to professional rebuilders who do this all day long. We have set a policy at my marina that we will not install any rebuilt engine, only brand new, because we were getting 10-20% failures right out of the box. This is even from some of the top names in remanufactured engines.

I rebuild my own engines because I like to do it and feel I can save some money. (that may or may not be true in the final analyis), but I hold my breath for the first couple hundred or even thousand miles until I am a little confident everything is ok.

Here is the problem in just doing the crank. It could be cam bearings, or a galley plug, or so many other factors that you may not solve the problem. You have got to tear into the entire engine and make sure everything is to spec. Have new cam bearings installed and make sure they are indexed correctly, install a new oil pump, it is cheap insurance. Mike everything and make sure no bearings show any scoring. The teardown is going to be the thing that dictates what you fix. What oil and weight are you running?

Don