Engine mount lag screw broke - how to remove?

[JASinIL2006]

I pulled the engine out my I/O a few weeks ago. The lag screws used were apparently not stainless steel, as they were somewhat corroded and very difficult to loosen. One of the screws snapped, leaving a 1/2" stub sticking out of the motor mount. This is what it looks like:



I tried a couple of times to turn it with some vise grips (after rapping it with a hammer pretty hard), but the vise grips just started chewing up the stub that remains. I'd like to get this out with tearing up the motor mount, because the mount is engineered fiberglass and it's otherwise in good shape.

Any ideas of I might try to loosen this screw? The others were about 3 1/2" or 4" long.

Thanks,
Jim

 

[Scott Danforth]

Re: Engine mount lag screw broke - how to remove?

smack it harder?

 

[dingdongs]

Re: Engine mount lag screw broke - how to remove?

put a nut over the top of a size that will slide over the remains of the bolt.weld the two together in the centre.hopefully it will be removeable now.after that you may have to remove mount and start again.

 

[Frank Acampora]

Re: Engine mount lag screw broke - how to remove?

Go to Sears and buy a stud remover. It grips tighter, the harder you turn and is driven with regular socket drivers. Not too expensive either.

And the boat manufacturer was not being cheap by not using stainless. Stainless is weaker than regular steel.

 

[Bondo]

Re: Engine mount lag screw broke - how to remove?

Go to Sears and buy a stud remover. It grips tighter, the harder you turn and is driven with regular socket drivers. Not too expensive either.

And the boat manufacturer was not being cheap by not using stainless. Stainless is weaker than regular steel.

Ayuh,.... Most of 'em I've seen are just steel,... a few galvanized...

If ya got a Welder, a 5/8" or 3/4" nut welded on, 'n quickly quenched to not burn up the fiberglass is what I'd do...

 

[dtj]

Re: Engine mount lag screw broke - how to remove?

heat the stud before removing.

 

[Chris1956]

Re: Engine mount lag screw broke - how to remove?

Put a pipe wrench on it. They should turn it.

 

[JASinIL2006]

Re: Engine mount lag screw broke - how to remove?

Well, I'm going to try all these ideas. I just don't want lose what bit of screw I have exposed. I'll smack it, heat it, then try an impact wrench-powered stud remover and if all that fails, I'll see if I can find someone to weld a nut on it. I've got some time before the engine will be going back in, so I don't have to scramble.

Anything I can do to prevent this when I put in new screws? Coat them with 3M 4200 or something similar?

Thanks and I'll let you know how this works out,
Jim

 

[bruceb58]

Re: Engine mount lag screw broke - how to remove?

I would also be putting some penetrating oil in there like Kroil or PB blaster to help remove the screw.

 

[JASinIL2006]

Re: Engine mount lag screw broke - how to remove?

Good thought... I'll do that as well.

Thanks,
Jim

 

[Bondo]

Re: Engine mount lag screw broke - how to remove?

Well, I'm going to try all these ideas. I just don't want lose what bit of screw I have exposed. I'll smack it, heat it, then try an impact wrench-powered stud remover and if all that fails, I'll see if I can find someone to weld a nut on it. I've got some time before the engine will be going back in, so I don't have to scramble.

Anything I can do to prevent this when I put in new screws? Coat them with 3M 4200 or something similar?

Thanks and I'll let you know how this works out,
Jim

Ayuh,.... I'm guessin' that's what the last guy did,....


I've never had a screw hang up that badly, in Wood....

 

[JASinIL2006]

Re: Engine mount lag screw broke - how to remove?

I know this is an older thread, but I thought I'd post an update. I finally got around to trying to remove the engine mount lag screw that had snapped off. There was about a half inch of the screw protruding from the fiberglass engine mount. I found a stud extractor that I attached to my impact wrench, and got a really good bite on the screw shaft.

Despite using penetrating oil and banging on the screw a few times before using the stud remover, the screw would not budge and actually snapped off again, this time flush with with motor mount.

Since I didn't many other options, I decided to try to drill out the screw. I didn't really expect it to work, but I started with a new, sharp 9/64" bit and I was able to drill right down the middle of the lag screw. (Actually, it was pretty slow going, and I needed a lot of oil to keep the bit cool, but it worked.) I then used drill bits of gradually increasing size, reaming out the hole and then using a larger bit. I got to a bit that is within 1/16" the diameter of the screw, when the bit cut through one side of the remains of the lag screw and started cutting fiberglass.

The hole I have for the motor mount is now the same diameter as the others, but it's center is about 1/16" off where it was before. I'm think that might not be a problem, and I'm hoping that the remnants of the lag screw (which essentially form a partial sleeve on one side of the hole) will still allow a new screw to bite and hold. At this point, I'd rather not have to cut away the motor mount and rebuild it; it's a big hunk of engineered fiberglass it would not be an easy piece to recreate.

I'll probably try shooting a lag screw into the existing hole before I do anything else to see how well the new screw seems to bite.

I don't know what was on the previous lag screws, but they were a bear to remove!

Jim

 

[UncleWillie]

Re: Engine mount lag screw broke - how to remove?

Seeing how the hole is already a mess and off center;
You might want to think about opening it up to remove the old bolt material and expose clean glass.
Then fill the hole completely with Glass bead and fiberglass resin. (AKA Glass Peanut Butter.)
Finally re-drill a new clean hole where it is supposed to be.

 

[jigngrub]

Re: Engine mount lag screw broke - how to remove?

Put a pipe wrench on it. They should turn it.

^^^^^ That ^^^^^^

 

[Frank Acampora]

Re: Engine mount lag screw broke - how to remove?

you now really have a couple of options: First open up the hole and center it. Then, you can either fill the hole with fiberglass strands (Kitty Hair) and EPOXY and re drill it to correct position and size. New fiberglass work does not stick to old cured resin as well as epoxy.

OR--You can use an expanding bolt anchor. OR--screw in a heli-coil or other brand thread repair. (Personally, I don't remember the other brand name, but I like it better.) The expanding anchor is dangerous as it may crack the fiberglass structural member.

You even have the option of gluing in a stud and using a locknut on top of the motor mount

 

[jigngrub]

Re: Engine mount lag screw broke - how to remove?

I figure there's got to be some kind of composite material in there holding that bad boy. I say keep drilling it out until you can center the bolt again, then fill the hole with a pourable marine epoxy like PC 11 or Loc-tite marine epoxy... both can be drilled and are tappable.

 

[smokeonthewater]

Re: Engine mount lag screw broke - how to remove?

Keep drilling until the entire side of the bolt is gone... then a hammer and punch can be used to dislodge/ break up the rest of the bolt.... pull pieces out with long tweezers.... once ALL metal is out of the hole, proceed as stated above with epoxy and filler and redrill the hole

 

[JASinIL2006]

Re: Engine mount lag screw broke - how to remove?

Consensus seems to that the rest of the screw has to come out, that it's not going to work if the hole is 1/16" off center. If that's the case, I think I'll try to find a small-diameter hole saw to enlarge the hole and remove some mount material along with the remnants of the screw. Using larger bits down the current hole is just enlarge the hole away from the side of the screw that remains; the drill bit slides toward the material with the least resistance - the fiberglass - and doesn't take out any more of the screw.

If I fill it the hole with epoxy (e.g., PC 11) can I use the same chopped strand that I use when making peanut butter? (I haven't worked much with epoxy, just poly resin.) Also, I'll flare out the bottom of the hole a bit to key the epoxy plug in, so it's got even more of a mechanical bond.

Thanks for the help,
Jim

 

[frantically relaxing]

Re: Engine mount lag screw broke - how to remove?

Yup on the holesaw, just cut the old bolt out--

Now, I'm not sure of clearances, but if you HAVE enough clearance, I would install THESE instead of just lag bolts:

You can glass the new one into your fat hole, and I'd do the same with the others too. Put a little anti-seize on the machine threads and you're done.

--IF you have room for the studs to stick out!

 

[UncleWillie]

Re: Engine mount lag screw broke - how to remove?

... New fiberglass work does not stick to old cured resin as well as epoxy...

Old, and even newly cured, fiberglass resin has a surface sealing wax inherent in the resin.
The trick when laying up fiberglass is to do it in one operation.
Unless you are using special layup resin that cures with a tacky surface; you can not expect to get good bonds if you allow one layer to cure before adding more.

Unless the current surface is removed before adding more layers, the new layers will not bond to the old glass.
As long as the old surface is removed and rouged up, new glass will bond just fine.

All this drilling and gouging will produce an ideal surface for bonding to when refilling this hole.