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Nissan ns3.5a Broken Bolts

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bwhiddon

New member
I bought a used ns3.5a outboard. It appears the previous owner never changed the zinc. It's corroded in its pocket. So I tried drilling and chiseling it out, but the prop shaft was in the way. So I figured I would drop the gear case from the drive shaft housing, and pull the prop shaft out for better access to the old zinc.

The bolt on the leading edge holding the gear case to the shaft housing broke,




leaving nothing to grab. So I tried the second bolt - under the gear case just behind the zinc pocket - figuring if it broke, I would at least be able to pull the thing apart and use vise grips to remove the broken screws.

It did break, but now the gear case WILL NOT separate from the drive shaft housing.



I've tried a rubber mallet and heating. I had assumed that the bolt sleeves would only be threaded in their lower halves. Am I wrong? Are these bolt sleeves threaded all the way through - or do I just have so much corrosion I will have to heat more and strike harder?

Any help is appreciated, because I am definitely at a stopping point here.
 
Those are 6mm SS bolts, with 10mm hex heads (cap screws). They thread into the far housing only; The near casting is not threaded. No doubt there is a lot of corrosion involved. Heat will not help, and will cause other problems; You need a rubber mallet, technique, and patience.
 
if you can drill the SS bolt then I'd try a screw removal tool, they come in several sizes and are quite cheap, they're counter threaded, in other words they tighten by turning anti-clockwise so that as you tighten it into the hole you just drilled it cuts a thread and as it gets tighter it's putting torque on the bolt to unscrew it. Before drilling the bolt I'd use a centre punch and TAP it ferociously quickly top and bottom, lots of vibration with liberal WD40 etc. to give it every chance to loosen.
 
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