How to remove bolt with no head

[xpertski]

Hi all,

It’s been a while since I’ve been on here with winter and my wife having a baby last October. I’m now, with lockdown, able to have some time to do some boat work.

I’ve come across a problem I hope someone can help with. There is an anode below the engine bracket on my Mercury Optimax 175, when removing the anode (it has two bolts) I removed one fine, the next the head came off. The bolt is so jammed, using locking nuts, grips etc didn’t work and eventually the bolt that was left sticking out also sheared off. I tried drilling a concave to use bolt removal drills - no joy. Now I have a concave hole and no idea how to remove the remaining bolt. I have thought about drilling it out and trying to use a tap and die set to make new thread, but how to do this with engine so close to the hull without room to turn a handle? Alternatively would it be sufficient to hold the anode in place using the single other bolt?

Thabks!

[Takson]

If you drill to the bottom of the bolt with an undersized drill, it can release the pressure and you may be able to remove the rest of the bolt.

If that doesn’t work you could drill out, retread then use a help-coils to re-bore the new hole to the existing size.

They are amazing little thingies.


https://www.abbottfasteners.co.uk/pr...yAAEgI9S_D_BwE

A quick eBay search brought this


https://www.ebay.co.uk/itm/402198693296

[Ribtecer]

Hi Xpertski

Glad you are still progressing with your project, shame about that bolt.

Looks like you have done a great job drilling out the broken stud, stainless in ali that's not easy.

If it's as good as it looks in terms of accuracy, can you not keep drilling to the depth of the other hole with a drill bit 1mm or so less (maybe 2mm 1st) than the original bolt and retap the thread?

Hope that's possibility, then fill them holes with waterproof grease.

Hope to see you afloat on the Solent soon.

Ribtecer

[Allye]

I’d agree with above, you’re only choice now is to drill all the way through, left handed bits and extractors would be a waste of time on that I think. Looks to be plenty of meat left so you could even over size it. Just don’t snap the drill bit! Just the worst.

[xpertski]

Thanks guys! I’ll try drilling all the way through and seeing what happens with that - will feed back tomorrow after another day of tinkering!

[spartacus]

I know this doesn't help now, but this is great video on siezed powerhead bolts.

https://m.youtube.com/watch?v=N4Lbwr35SU4

It's in a sod of a location too under the saddle. Is another option just to abandon trying to drill out what's left of that sheared bolt and look to drill a new hole instead, say 20-25mm in from the broken one and tap that instead? On your new zinc anode, you'll just need to drill a new hole for the bolt. You could fill the hole you're currently drilling with epoxy.

[breezeblock]

My preferred method for this type would be to weld a washer around the remainder of the bolt with tig build it up to a nipple then weld a nut onto it do not use easy outs on this type of repair be warned a 90deg drill and retap it if you can get it accurately centred is another good method if it does go shit shaped helicoils would work quite well

[craig_c]

I would try drilling it but I've had a similar issue in the past and drilling stainless is a complete NIGHTMARE.

Using one bolt would be fine if the thread is good.

Spartacus's suggestion of drilling another hole and one in the anode would be a great fix if your not confident with one bolt. at the end of the day the anode is a sacrificial part and a consumable so one more hole in it won't affect its lifespan

[Davie]

Originally Posted by craig_c

I would try drilling it but I've had a similar issue in the past and drilling stainless is a complete NIGHTMARE.

Using one bolt would be fine if the thread is good.

Spartacus's suggestion of drilling another hole and one in the anode would be a great fix if your not confident with one bolt. at the end of the day the anode is a sacrificial part and a consumable so one more hole in it won't affect its lifespan

Don’t need to drill a hole in the anode, the genuine part comes already pre-drilled, wonder why?

[paintman]

Anode held on with two bolts.
One bolt shears leaving a well stuck bit blocking that hole.
Spartacus suggests instead of lots of work getting the sheared bit out just drill a new hole in the mount next to the blocked one & thread it.
The new hole isn't going to line up with the hole on the new anode so you need to drill another hole in the anode to line up with your new hole.

[Salty Pete]

This advice will probably be too late. But when removing a bolt especially in aluminium, if the bolt does not undo easily, apply heat to the head or any thread sticking out, with a small blow torch. This will expand the bolt and push the corroded aluminium out.

Allow the bolt to cool and it should then be loose in the thread.

A dash of WD40 for lubrication and the bolt should undo fairly easily.
Don't forget to tap the thread out to clean it and anti-cease compound on the new bolt.

[smiffy422]

Hey,

i work most days with ali jet drives and the stainless bolts always corrode in like you have had.

Get your self on amazon or ebay and buy a Heli coil set.

Drill the bolt as far as you can like you said and then once the kit comes it will have the correct size drill bit and Tap for you to thread the hole.

you then spin in your stainless coil and your hole is back to the original size and now your spinning your stainless bolt into stainless threaded hole so next time it will come out far easier.

id suggest drilling and threading both holes to make life simple next time you change your anodes

[Salty Pete]

Heli coils are great the first time. But if your bolt seizes in the Heli coil later, it more difficult to remove. They are good and I've used lots of them but they can be a problem later.

[beamishken]

If your gonna drill & helicoil, probably best off locktighting a stainless stud in & using stainless nuts to secure your anode your then running stainless on stainless so corrosion should be less of a problem