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Old 23 February 2009, 13:39   #1
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Snapped bolts on ali outboard block

As far as bad days go, this one is fairly well up there. I have managed to snap not one, not two, not even 5, but a depressing 10 bolts off while trying to get them out. (hhmm, thats a new smiley since I was last around)

I won't go into why I felt the need to go on this rampage of bolt snapping brutality, perhaps my DIY mechanical mind had turned to mush after a year of no ribbing and dossing around in canada or maybe I was day dreaming of hot summer days and glassy flat seas while each bolt went crack under surprisingly little load

Anyway, the engine as many of you will know is a 70hp tohatsu 4-stroke (1996 if I remember correctly) and I was trying to take the plate off the side to gain access to the cooling ducts that feed the tell tail so I could unblock it all. Each bolt screws through the plate, a gasket, a spacer plate and then another gasket (as far as I can tell) before screwing into the block. Each bolts appears to have snapped at the point where the plate meets the first gasket so if I do get the plate off there should be a little stump of each bolt left.

The plate is still on because there are 4 bolts at the bottom that I have not yet touched. If I snap these off too then the plate will come off but I would need to strip the engine and take the block off to access the broken bolts with a drill. For this reason I have left these intact and am hoping to get all the other broken bits out, stick new bolts in and unblock the cooling clog by some other means.

Does anyone have any experience of snapping bolts off and how did they get the bits out? Over the next few days I'll be squirting everything with plusgas but I have a feeling it won't be enough. I really don't want to have to buy a new engine because of this, not that I could afford to anyway.

I think I've probably thought of every possible option but the knowledge on this forum never ceases to surprise me so thought I'd give it a go.

Thanks in advance
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Old 23 February 2009, 13:47   #2
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Blow lamp and mole grips
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Old 23 February 2009, 14:03   #3
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Some photos would be great.

What size are the bolts?

You may need to snap them all to take the cover off - then either the mole grips or maybe even put slots in them and use an impact driver.

Another solution is to run a die down them the opposite way and stick a nut on them.
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Old 23 February 2009, 14:51   #4
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Tap (hit) the ends of them to shock the dross around the threads and attempt to make just a little space to break the seize.
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Old 23 February 2009, 15:00   #5
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bolts are 6mm.

Considered the heat option, but not sure how far I can take it though before melting or distorting something. Using mole grips obviously means I need to get the plate off which will probably result in the other bolts being snapped as well.

Whats an impact driver? Dad and I were just discussing the options with respect to using tapered stud extractors and have come to the conclusion that the one of the most difficult things will be drilling a decent straight hole to begin with.

Thanks for the replies so far
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Old 23 February 2009, 15:04   #6
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Quote:
Originally Posted by Dirk Diggler View Post
Blow lamp and mole grips
Its the way to go also spray with easing oil.If you use heat gun instead of a blow torch it will be better and heat the ali and hopefully it will then pop off
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Old 23 February 2009, 15:07   #7
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http://www.screwfix.com/search.do?fh...NJ1Q&source=aw

But make sure you get decent bits to go with it.
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Old 23 February 2009, 15:14   #8
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Welcome back Tim, I hope the trip was all you expected, I'll have a look on your website later to see if you've uploaded any images of the last year.

Regarding the bolts, and to answer your specific question, I've had lots of experiance snapping bolts off
You know you have to do it properly, and that I'm afraid involves trying/breaking the other 4.

Once the plate is off, if you have a little stub of each one you can soak it in WD40 or Plus-gas for a few days then grab each one with a pair of mole grips to carefully wind it out.

6mm isn't very big to use a stud extractor with a left hand thread, you'll only be able to drill a 3mm hole and use a very small extractor, which in my experiance will snap off and leave you with a bigger problem as you now have a very hard piece of metal stuck in the hole.
You'd be far better off drilling out bigger in the first place and heli-coiling the holes.

Don't be afraid to remove the powerhead, it's really not that big a job to sort your problem out properly.

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Old 23 February 2009, 15:15   #9
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Believe me, we do this all day long, heat and mole grips, and as peter says, a squirt of oil, we prefer wd40, but that's coz we buy it by the barrel load.

Get the burner on it, and get it really hot, it won't do any damage, it doesn't even harm the paint on a merc!
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Old 23 February 2009, 15:17   #10
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Originally Posted by codprawn View Post
Another solution is to run a die down them the opposite way and stick a nut on them.
That ain't going to work, you'd need a pair of nuts so as to be able to lock them up.
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