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Getting broken bolt out of engine block

wannabecraig

One of the two bolts that hold my starter motor in place on my 3trl boat engine has broken inside the engine block. This is on the underside of the engine, about 6" from the floor, so I can't get a drill at it to drill out the bolt. If I were to drill it out, I'd have to remove the engine,. This is a nightmare and I'm not up for it.

I was thinking of putting in another screw with Araldite for steel or Gorilla Glue Epoxy on the top and hoping it would catch the broken piece of the screw and bond, then I could remove the screws.

Is this likely to work? Do I have any other options?

TIA

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BorneTobyWilde

Could you not drill straight through, from top, put a bolt and nut on it then

BorneTobyWilde

I'd drill it from top, put a stainless 10mm bolt and nut on it.

The Continental Op

OK so I think I understand this now?

The bolt goes in vertically from underneath and the threaded hole is inside the big chunk of cast iron on the side of the engine.

The Continental Op

BorneTobyWilde wrote: »

Could you not drill straight through, from top, put a bolt and nut on it then

Good idea but I think it needs a good bit of preparation and thought?

I'd consider grinding a flat where you have put the arrow first to get the drill started and then perhaps grind a curve back when finished for stress relief.

Its going to need careful centering and I would start off with a small pilot hole. Long drills are going to be needed to drill a straight hole.

Also as you suggest no need to thread the hole as a nut on a long bolt will secure it.

stratowide

The Continental Op wrote: »

OK so I think I understand this now?

The bolt goes in vertically from underneath and the threaded hole is inside the big chunk of cast iron on the side of the engine.

Ah yes thats it I think.Bolt and nut so if he doesn't mind drilling that plate.

Tokyo

BorneTobyWilde wrote: »

I'd drill it from top, put a stainless 10mm bolt and nut on it.

Looks like it will have to be drilled at an angle though, through what looks like a couple of inches of cast iron, plus presumably through the remnants of the bolt stuck in the block, and hopefully all will line up.

Best case scenario, it will be an awful bodge of a job, and not one easily undone in future should he lift the engine out and want to set it right.

Not my engine, but if it were, I'd be looking at making some kind of bracket using other existing bolts or bolt holes on the engine block, or possibly welding a tab onto the starter motor and bolting op the starter for now until opportunity to lift the engine out. Though if an engine hoist could be borrowed, I'd probably just bite the bullet now. Engine doesn't have to be lifted out completely, just enough clearance to get access.

The Continental Op

Certainly not a job to be undertaken lightly.

The Continental Op

OK so here is how I'd go at it Plan A, B and C.

Assumptions: The bolt broke off in service therefore the piece that still needs to be removed isn't rusted in place. Looking at the bit of the bolt that came out that isn't too much of a stretch.

Plan A drill out minimal size hole in the bolt from below and use a small extractor using very little torque. If that fails go to Plan B

Plan B drill out a the original hole making it larger so you can use the max size extractor and apply a lot more torque, but still not over doing it.

Plan C is to go down from the top.

So for Plan A or B you need to be able to get a right angle drill in under neath something like https://www.amazon.co.uk/DeWalt-Lithium-Ion-Cordless-2-Speed-Batteries/dp/B0051HE3XC/ . Now if you have only an inch to spare then you can grind the shank of a drill down to shorten it so you can get a start. The key to this is to use a guide in the hole to make sure the drill is drilling into the center of the bolt. As an illustration this is something like you need https://www.amazon.co.uk/Woodworking-Drilling-Oblique-Positioner-Locator/dp/B07D9LSWPH/ a round section with a hole in the middle a little bigger than the drill bit you are using. The guide needs to fit nicely into the hole. I'd start with a 2mm hole and be very very careful not to break the drill bit off in the hole (nightmare!!) go in no more than 15mm then try gently with an extractor. If that doesn't get any movement now you have a pilot hole you can drill out to say 5mm or even bigger. The size of drill you use will probably be dependant on the size of guide you can find. Best not to try this without a guide!

Plan C is as already mentioned from the top.

Some good info here

wannabecraig

stratowide wrote: »

No its the semi-circular plate directly under the starter.Will that come off..?

Have you had the starter actually out or is something still holding it..?

Is there any access from the other side i.e. gearbox,bell housing or drive train..?

I cant take taht plate off no, part of the engine.

I can take the start off, it's currently being held by the other nut, long nut on the other side.

There is no access from the back.

The Continental Op

wannabecraig wrote: »

I cant take taht plate off no, part of the engine.

I can take the start off, it's currently being held by the other nut, long nut on the other side.

There is no access from the back.

Think we are passed that now anyway provided we have got the position of the bolt right. Its all down to how much access you have to it under there.

wannabecraig

I don't want to drill into the engine, happy to take it out, or get it taken out, I just can't get anybody to do it soon.
I really want to try to get the screw out, so I'm going to go with plans above.
Spoke to a mechanic today and he warned me about drilling blind into that screw, said Really want to make sure
it doesn't go into the block itself. But I might just take a shot!

Instead of buying an angle drill, would this do? https://www.screwfix.ie/p/erbauer-angled-bit-holder-160mm/9929v

Will go through video above and see if I can get it done that way.

Really grateful for all advise so far, lots to work on.

wannabecraig

The Continental Op wrote: »

OK so I think I understand this now?

The bolt goes in vertically from underneath and the threaded hole is inside the big chunk of cast iron on the side of the engine.

Yes, this is exactly it, sorry for lack of clarity.

wannabecraig

BorneTobyWilde wrote: »

I'd drill it from top, put a stainless 10mm bolt and nut on it.

It that not a little extreme? It's fixable, I just want to give it a small pop myself before I have to pay to get the engine taken out.

The Continental Op

wannabecraig wrote: »

I don't want to drill into the engine, happy to take it out, or get it taken out, I just can't get anybody to do it soon.
I really want to try to get the screw out, so I'm going to go with plans above.
Spoke to a mechanic today and he warned me about drilling blind into that screw, said Really want to make sure
it doesn't go into the block itself. But I might just take a shot!

Instead of buying an angle drill, would this do? https://www.screwfix.ie/p/erbauer-angled-bit-holder-160mm/9929v

Will go through video above and see if I can get it done that way.

Really grateful for all advise so far, lots to work on.

The problem with that is where is the chuck to hold a drill? You'll need to get some suitable size drills with a hex head on them an example https://www.amazon.co.uk/LESOLEIL-13pcs-1-5-6-5mm-Titanium-Coated/dp/B01D30D2IA/. The downside is you can't sorten the shank on them.

However you do it you need some form of guide, because you can't see what you are doing but I suspect you can check if you are drilling squarely into the bolt.

BorneTobyWilde

wannabecraig wrote: »

It that not a little extreme? It's fixable, I just want to give it a small pop myself before I have to pay to get the engine taken out.

No harm in drilling it from top, it's just steel. Grind it more flat, and a tad wider. Use small bit and drill straight through, use bigger bit as you go to widen it until it can take a bolt.

It's not the correct fix, but done right it's a solid one. Need pro cobalt bits.

Best to try everything else first. Who knows it might come out easy.

greasepalm

Have you tried the easy way yet with starter motor removed?

wannabecraig

greasepalm wrote: »

Have you tried the easy way yet with starter motor removed?

NO, I'll be trying this on Monday. I've never done this before so being cautious.

wannabecraig

The Continental Op wrote: »

The problem with that is where is the chuck to hold a drill? You'll need to get some suitable size drills with a hex head on them an example https://www.amazon.co.uk/LESOLEIL-13pcs-1-5-6-5mm-Titanium-Coated/dp/B01D30D2IA/. The downside is you can't sorten the shank on them.

However you do it you need some form of guide, because you can't see what you are doing but I suspect you can check if you are drilling squarely into the bolt.

I have a drill set with HEX heads but I can go an buy a decent metal on too.
https://www.screwfix.ie/p/dewalt-hex-shank-cobalt-hss-drill-bits-8-x-117mm/3713v
It's a M10 bolt in there so not sure this is the correct size

gutteruu

Might be a bit rough, but can you just put a few spot welds on the side the bolt is broke, holding the new starter to block (being careful not to crack block with heat). Could always just grind them off next time the engines out or you want to change it. Hard to see how you'll get it out if its lodged well in there and you've only 6 inches to play with.

listermint

Surely hoisting it out a foot or so is the smartest option. You should get to grips with your engine back to front as there's no marine mechanics with you out on the water. Taking off the drive unit and other bits and lifting it will get you more acquainted with the workings.

The Continental Op

wannabecraig wrote: »

I have a drill set with HEX heads but I can go an buy a decent metal on too.
https://www.screwfix.ie/p/dewalt-hex-shank-cobalt-hss-drill-bits-8-x-117mm/3713v
It's a M10 bolt in there so not sure this is the correct size

afaik thats 10mm at the widest part of the thread and about 8.3 (ish) at the narrowest where the threads sticks in.

Drilling with an 8mm drill is a bit courageous to my mind. You can't fit any guide in to stop you drilling off center and will probably drill into part of the thread. Assuming you don't go off line altogether. I suspect a hex chuck will also be a bit wobbly. Then you'll be left with swarf and a thin bit of bolt to get out which won't come out easy.

Its a compromise over drill size, really small is a good start but small drills snap easily. A large 8mm drill might not even bite with the pressure you can put on it in that location. I'd go with say a 3mm drill bit (get a spare) use a guide of some form (ideally 8mm diameter with a 3mm hole down the middle) and take it really easy. Who cares if it takes an hour to drill a 3mm hole 15mm deep. Some form of cutting lubricant would also help. Take great care not to twist the chuck so you don't snap the drill. Once you have a bit of a hole you can try a stud extractor. Then if no go your small hole can easily be made bigger and because its in the middle because of the guide you can them if you must go to 8mm but I'd go to say 4 or 5mm and use a bigger extractor. Do beware if you go up through drill sizes in small increments there is also a possibility of breaking a drill if it bites to hard in the side of the previous hole so again take it slow and easy.

wannabecraig

listermint wrote: »

Surely hoisting it out a foot or so is the smartest option. You should get to grips with your engine back to front as there's no marine mechanics with you out on the water. Taking off the drive unit and other bits and lifting it will get you more acquainted with the workings.

I can do this after trying with it in situ. There are a load of other complications, like getting the boat out and having an engine crane.

listermint

wannabecraig wrote: »

I can do this after trying with it in situ. There are a load of other complications, like getting the boat out and having an engine crane.

Why take the boat out and why engine crane ? Can it not be lifted with with a conventional mechanical or electrical winge / pulleys.

depcon

If you are going down the drill bolt extractor route, a centre drill used on a lathe might be an option to start the hole they are fairly short . Also a spring loaded centre punch will give you an intial dimple to start the drill. But as said above take it slowly and use cutting lubricant . Maybe try drilling the sheared piece of the bolt first to see how it goes first.

The Continental Op

depcon wrote: »

If you are going down the drill bolt extractor route, a centre drill used on a lathe might be an option to start the hole they are fairly short . Also a spring loaded centre punch will give you an intial dimple to start the drill. But as said above take it slowly and use cutting lubricant . Maybe try drilling the sheared piece of the bolt first to see how it goes first.

Thats good thinking, even better if the OP can find one with a shaft about 8mm thick. But does rely on having a good bit of depth to the hole before you get to the broken section.

Sharpyshoot

We use tig and filler rod to add to a sheared bolt. Build up so can grab with a moles grip. The heat from the tig looses out the seized bolt end too.
Urinating around with wd40 and flexible drill shafts and other nonsense is a waste of time.

The Continental Op

Sharpyshoot wrote: »

We use tig and filler rod to add to a sheared bolt. Build up so can grab with a moles grip. The heat from the tig looses out the seized bolt end too.
Urinating around with wd40 and flexible drill shafts and other nonsense is a waste of time.

How do you avoid welding to the sides of the hole?

wannabecraig

Sharpyshoot wrote: »

We use tig and filler rod to add to a sheared bolt. Build up so can grab with a moles grip. The heat from the tig looses out the seized bolt end too.
Urinating around with wd40 and flexible drill shafts and other nonsense is a waste of time.

Cold this be done with the engine in place tough? Given lack of decent access?

Sharpyshoot

The Continental Op wrote: »

How do you avoid welding to the sides of the hole?

Don’t leave a rooter at it.

stratowide

Sharpyshoot wrote: »

We use tig and filler rod to add to a sheared bolt. Build up so can grab with a moles grip. The heat from the tig looses out the seized bolt end too.
Urinating around with wd40 and flexible drill shafts and other nonsense is a waste of time.

Its a 10mm bolt sheared off in a position that can only be seen with a mirror.

I wouldn't even plug in the welder let alone try to weld something onto it.