1976 Evinrude 55hp: Frozen bolts in exhaust housing

[TLewis]

I 'm rebuilding a 1976 Evinrude 55hp (Model #55673) engine. Despite my best effort to avoid damaging the outer-exhaust-housing (long-version pn#320316), I busted a few bolts off. The exhaust housing now has a few broken bolts (two on one motor mount, and two on housing-to-adapter). There's some excessive powdery white corrosion build up around each bolt and some down into the threads on the ones I managed to get out.

My exhause housing is obsolete now.

A couple questions:
1) Does anyone know how to track down a new or used exhaust housing (pn#320316)?
2) Can anyone suggest a cost effective method of removing the corroded bolts? There's about 1/4 of the bolt exposed in all cases. My first instinct is to put heat and a pair of vice grips on it but I have resisted so far ...
3) Can someone tell me what these bolts are made of? The heads sure twisted off easy.

Thanks

 

[Daviet]

Re: 1976 Evinrude 55hp: Frozen bolts in exhaust housing

Heat is your best bet, be careful not to melt anything. The bolts should be stainless steel, some one may have installed improper bolts at some time.
Next option, drill out the bolts, you can install heli-coils if you mess up the threads.
The white stuff icorrosionon, use antseizeze when you put it bactogetherer.

 

[PNW Driver]

Re: 1976 Evinrude 55hp: Frozen bolts in exhaust housing

My 115hp was all corroded up. I broke a few off. I used heat and vice grips. They came out easy. I heated the surrounding metal not the bolt.