2.5 Mercury broken head bolts.

[leifbert]

I am hoping to get some advice from you guys. I broke two head bolts in the process of replacing a head gasket on my 1992 XR6. They are broken flush with the block. What's the best way to get them out? Thanks.

[Dave Strong]

Drill them and use good quality bolt extractors.

Dave

[outasite]

You said they are flush! Most will break just a little below the deck,leaving you enough room to use a centering drill bushing witch is a big help

[toyomirage02]

use some heat, good drill bits and maybe a good easyout, atleast ya only had a few my neighbor today took aprt his 120 omc and he broke all on one side, he drilled around every one and we still had to beet it off the motor with a sledge and a pipe on the t-stat houseing,what a mess

[Dave Strong]

If you can trim up the motor and get some good penetrating oil to soak the threads, then drill and remove the bolts. Had a 2.5 245hp that had casting void and would let water on the head bolt threads on one cyl, sealed it with JB Weld and was OK after that.


Dave

[flabum1017]

When you drill, drill slow. I found using regular HSS drill bits with a spray bottle of water is easiest. I never had any better luck with cobalt bits, always used the HSS bits turning real slow allowing the curl to be continuous. A drill press is best if you have one. With these salted up motors, I never had any luck using extractors, they will actually enlarge the broken bolt as they grip wedging the bolt even tighter in the hole. I usually drill them out, and put Helicoils in. To get the broke bolt center dimpled, it's easiest putting the head back on and using the largest drill bit that will fit the bolt hole and dimple the broken bolt. Pull the head back off and use smaller bits to start drilling.

[faztbullet]

Grainger has some left hand drill bits that work nice in a electric drill, not much luck in cordless as chuck dont like to stay tight.

[mn808gade]

use a transfer punch/or a drill blank,with the head bolted on to get the center.using a "home made tool"(1x1 inch square alum tube),drill a hole,same size,in a drillpress,TO KEEP THE BIT STRIGHT.drill all the way thru broken bolt,to the bottom.use left hand twist bits.keep it cool,dont hog it,use cooltool/cutting lube/or some such other metal cutting lube.go slow go straight.-th

[eddieneal1292]

Gm exhaust manifold bolts usually break off flush with the aluminum head. We carefully grind whats left of the bolt and weld a washer and nut to it with a mig. I know the drilling thing sucks. Usually the heat from the welder is enough. Maybe you can give that a shot?

[Dave Strong]

If this was a salt water motor, well I wouldn't want to be you.

Dave

[mn808gade]

when I worked in San Diego,broken/salted bolts were .5hr per bolt.sometimes a rebuild had 20+ bolts.-th

[LongShot]

+1 on welding a washer and nut to them. Drilling them out with a hand drill sucks. If your doing it in situ forget the drilling. If I have a block on the bench with broken bolts I use a tap burner. Slick as snot. Burn a hole right through the bolt and drill with lh drill.