Getting broken bolt out of engine block

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

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.

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.

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 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 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.

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

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.

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.

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.