I figured it would come out easy too...but no dice so far. Tried an extractor but scared to break it....been being patient with the penetrating oil.

If bolt is being a total pita.It may make sense to just pull motor and do it,before ruining block.Not hard to pull most boat motors .JMO

Possibly try drilling the hole 1-2 sizes larger but still within the thread size so you don't damage them. You s/b able to then insert the easy out further since most are tapered. I'd work every angle I could think of before even considering pulling the motor.

This thread started on 5-14.Here we are almost two weeks later ,working upside down trying not to pull the motor .How much time has been wasted trying not to pull motor .Good luck with whatever you decide to do

motor coming out today. Bolt must have bottomed out and still has tension. Unfortunately when I drilled it, I did not get the hole exactly centered. Gonna make this job tough. I'm not sure what to do now. Gonna be tough to re-center the hole now. thinking about welding a nut to the bolt, but if it doesnt work I will have the previously drilled hole filled full of tough to drill filler metal. Also worried that with a hole in the bolt that is close to the threads, that it might weld the bolt threads and block threads together.

However you go about getting it out it will be a lot easier looking down on it instead of trying to drill a centered hole upside down ,in a mirror.Not to be a bummer ,but if you had pulled motor to began with, the hole would probably be center of broken bolt and stepping up in bit size would be a possibility and bolt would be out .This thread may be a wakeup call for anyone else trying to work on their head just to not have to pull motor
At this point i think getting someone that is skilled at welding to weld a nut on may be best chance of success....Providing there is enough there to weld to.
If nothing else you can now take motor to qualified machine shop and they can see what they are working with .
just my opinion
Good luck .I hope it all works out

I understand ur frustration.....this task is tough but it can be done, I've done it 2x, once on my boat and prior to on another friends boat. Wouldn't have suggested it if I didn't think it was possible. If in fact the bolt has bottomed out, yes it wil make it tough but regular starter bolts aren't going to bottom out mounting a starter into the block. Go back w/grade 8 bolts and youll have less likely the chance of them breaking. Sorry this route wasn't helpful. Good luck.

Make yourself a drill guide out of a block of steel with two holes that are on center with your starter. one hole should be a tight clearance for the bolt usually the same size drill will work with about .0015" clearance. The second hole should be your tap drill size. Bolt it on, line it up, make sure it's clamped tightly, it will probably require a second clamp, and drill out the old bolt. I used to do this all the time when I did a stint as a tool maker.

If you are looking at it on an engine stand now, use a hammer and punch to back the bolt out. You punch around the circumference ccw. The hammer blow tends to get things moving. As far as what causes broken starter bolts, my first though is always hydrolock.

Good idea! fortunately I didnt have to go that far. Pulled the motor and mig welded a nut to the bolt...came right out. Really depressing that the motor had to be pulled to remove a dammn bolt. On the plus side, I did a bunch of service work while it was out. Changed plugs, installed the oil drain hose that I was planning on doing soon, got the bilge nice and clean, and treated some corrosion on the motor. Just got back from an overnight trip, all is well. Thanks for all the replies guys. Happy boating!