Checkmate454Mag hit it on the head. On the late 80's Convisor the stringer in the motor compartment is covered by the sole plate on the outside portion. This make it very difficult to thru bolt the front motor mounts, in order to do this you must cut an access hole in the sole. I concidered this option but I am not sure I want to do this. I currently run 600+ HP thru the stock MERC mounts

If you don't want any prob. down the road do whatever it takes to through bolt the motor mounts. Just some advice from a guy that runs in a lot of big water. If you like to run on rivers and ski lakes don't worry about it.