Help with broken bolts

[john8504]

Starting to tear down my 1952 evinrude 3 hp by taking the head off to replace piston rings. Low and behold I find myself with 3 broken head bolts. One is flush and the other two have a little grab. Anyone have a remedy? I’ve tried a propane torch and no luck.

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[david-bartlett]

Propane is usually not enough. I use a MAPP gas torch with good results. Get the stud HOT with the torch, then put a pair of vice-grips on the stud. This will act as a heat sink and shrink the stud quickly, often breaking the grip of the stud to block. Your favorite penetrating oil can’t hurt.

Oxy-Acetylene is best, but not all of us have that luxury. As for the flush one, center punch and drill it out. Start small and work out with bigger bits until close to the threads, then work it out with an awl or pointed screw driver.

Stay away from the exhaust cover screws if you can help it. Those break easier than the head bolts.

Good luck.

[Anonymous]

You can bolt the head back on and use as large a drill bit that will fit into the bolt hole to center the drill to get a centered pocket in the broken bolt and then remove the head and drill with a small bit and work your way up to a larger one until touching the threads.

[PugetSoundBoater]

quote XR55:

You can bolt the head back on and use as large a drill bit that will fit into the bolt hole to center the drill to get a centered pocket in the broken bolt and then remove the head and drill with a small bit and work your way up to a larger one until touching the threads.

I really like your method! Thanks for sharing.

"Some people want to know how a watch works, others just want to know what time it is"
Robbie Robertson

[Anonymous]

Use care that the large bit does not walk off center as the head is soft aluminum.

[20mercman]

If you have access to a TIG welder, I would weld on to the flush bolt. This will get you something to grab on to. Again, heat will be your best friend. Ox/ac will be best, but I have been able to use propane, as long as it has a big tip. MAP is hotter than propane. Once the bolt starts to move, go back and forth, and penetrating oil till it will come out. I had a Wizard 18 cid hurricane block that had 17 broken bolts or studs in it. Many of them flush or below the surface. I was able to get them all out this way.

Steve

[bobw]

First thing to do is wire brush all that corrosion away from the area where the broken bolt enters the block. This will allow your penetrating fluid to wick down into the bolt threads in the block. And use a quality penetrating fluid, not WD40. On the one long stub you could thread 2 nuts onto the bolt, jam the 2 nuts tight together then use a wrench to turn it loose. As with all broken bolts, this process takes judicious use of the torch, copious amounts of penetrating fluid and liberal amounts of PATIENCE. I once had 2 broken head bolts like yours and I worked on them an hour or so every night with the propane torch and fluid before they finally broke loose. Good luck.

Bob

1937 Champion D2C Deluxe Lite Twin
1954 Johnson CD-11
1957 Evinrude Fastwin 18
1958 Johnson QD-19
1958 Johnson FD-12
1959 Johnson QD-20

“Every 20 minute job is only a broken bolt away from a 3-day project.”
"Every time you remove a broken or seized bolt an angel gets his wings."

[bobw]

Forgot to say I worked on them every night for 2 weeks before they finally budged loose. PATIENCE!!

Bob

1937 Champion D2C Deluxe Lite Twin
1954 Johnson CD-11
1957 Evinrude Fastwin 18
1958 Johnson QD-19
1958 Johnson FD-12
1959 Johnson QD-20

“Every 20 minute job is only a broken bolt away from a 3-day project.”
"Every time you remove a broken or seized bolt an angel gets his wings."

[jcrigan]

A set of these are handy for centering your drill bits. They don’t enlarge the holes like a drill bit would.

[outbdnut2]

Be sure your cylinder head is absolutely flat before you put it back together. These 3 HPs are notorious for slightly warped heads that cause the head gasket to blow out a passage between the two cylinders. If it’s not perfectly flat, sand it on wetordry paper laid on a flat, non-flexible surface. I use the steel top of an old tablesaw for the flat surface. Tighten the pair of center bolts first. Torque spec is 60 to 84 inch-pounds.
Dave

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