Hi, The propshaft should run true at all times and not strike the stern tube, if you continue to run the boat you will cause damage. Check out the engine
mountings are correctly sized and replace if required, disconnect the propshaft from the gearbox
, check for 'play' in the shaft and if necessary slip the boat and replace the cutlass bearings.Grease the stern tube. Bolt the shaft to the gear
box flange loosely, turn slowly by hand checking the clearance between the 2 flanges is the same every 90 degrees, if not 'shim' adjust the engine gearbox to be exactly
in line with the shaft. Finally check all boats are tight, you should be able to turn the propshaft slowly by hand with no tight spots. Take a short test run, re grease the stern tube,recheck all bolts for tightness.
I hope this helps you.