Re: 1996 Force 120 has trouble starting
The machine shop work gets expensive.
If you cut through a water jacket, depending where it is, the engine may be junk as some areas are not repairable.
As for removing the bolts, at the street level, it is usually not possible. The reason is that the bolts, which are steel, have reacted with the case, which is aluminum. This causes what is called dissimilar metal corrosion. When this occurrs to a bolt in a recess, the buildup of corrosion usually locks the threads up solid. That is why the bolt fails.
Sometimes the bolt breaks in the case and sometimes the head of the bolt snaps (if they are inferior grade bolts). Even if you have some bolt shank available, you will probably not be able to turn it out even with vise grips and WD40, which is not a great penetrating oil.
There are special stud removers that you can try if the shank of the bolt is accessable. If you decide to try this, I would suggest using a penetrating oil such as "Kroil" and heating the case to try to draw the oil into the threaded area.
This is about the only technique open to you if you have the puller available. Snap On tools and MAC tools sell these stud removers but they were designed to insert and remove good studs from good blocks and may not work in this instance.