tap a stuck bolt?

I have a stuck bolt in my 1976 Evinrude 9.9 that I'm having a devil of a time with. It's one of the middle bolts that attaches the water jacket to the head.

I finally drilled a 1/8" hole in roughly the center of the bolt. I've been soaking it for weeks and periodically applying heat, I've been using an Easy-out to try and remove the bolt. I'm to the point now where I'm afraid I'll break the Easy-out and then I'll really be "screwed."

Since the water jacket is not under extreme pressure, and the location is such that the bolt will have good bolts on either side of it, should I just tap the stuck bolt and put a smaller diameter bolt in its place? For a 1/8" thread, it looks like the appropriate tap would be a 4 mm x 0.75. I would then replace the original bolt with a 4mm one and use a washer to hold down the water jacket. I could also use gasket sealant to help ensure a good seal.

Any thoughts are appreciated.

Thanks,
Jonathan

Re: tap a stuck bolt?

I just had the same problem on a 1981 50hp Evinrude. The three water jacket to cylinder head bolts that are in the center (I believe there were 14 in total) were snapped off when I got the motor. I couldn't save the bolts nor the threads so I tapped up one size and they hold well. I've only ran it on the stand, but I didn't see any problems. I think the originals on my water jacket were 1/4-20 and I tapped up to 5/16-24 if that helps.

Re: tap a stuck bolt?

A machine shop can probably extract it for you and save the original threads. I called a couple here in my area (Dallas, TX) and they quoted about $20 per screw. If you don't know a machine shop, call a local boat repair place to see if they can give you a referral to who they use. May be worth if for you since you only have 1 stuck bolt. I had mine done and back to me in 2 days. For me, it was better than fooling around with it for weeks trying to soak and heat to get it out.

Re: tap a stuck bolt?

Your best bet is a machine shop. Stay away from the easy-outs.

Re: tap a stuck bolt?

reverse drill bits work better than easy outs. Cheap easy outs should be called break off's because that's all they do.

Drill the bolt to the point that it is very thin but not into the threads. then you can apply heat and knock the bolt into itself. If you can get the very end of the bolt, then it should come easy.

Machine shop will do nothing more for you except charge for it, but if you can't get it, have the machine shop do it so it doesent get destroyed.