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Unbolting engine block. Bolts wont turn,should I snap them?

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Bestfishes

New member
I have a DT50 (1983) with an exhaust leak under the engine block. After removing some cover plates I have discovered that to remove the engine block I must undo 8 bolts from below. They don't want to turn and heating them with a flame torch doesn't look easy as the threaded parts of some of the bolts are unseen below the block.

Should I just snap the bolts and lift the block and try and remove the stuck parts of the thread later or is there another option I can explore without taking it to the marine mechanic?


Regards....Craig
 
Try a 50/50 mixture of ATF (auto trans fluid) and acetone on the bolts, let it sit overnight and then try to remove them. Sometimes trying to slightly tighten then loosen and repeat that some will free up stuck stuff.
 
Thanks turbojoe, I had been spraying with WD-40 without any luck. When the engine block is off I'm sure I'll be back here seeking more help. It's much appreciated.....Craig
 
Try PB Blaster.Then if you can get to them try thr PB and then tap with a hammer and then a bit of heat.Then repeat.
Like torbo says,try t o tighten a bit and then back it off.

I worked for an hour to get 1 bolt out and it was a 1/4-20.Some take a while some are just gonna break.
 
the only way to get them loose is to heat the surrounding aloy with a gas burner to appr. 100' / 150' Celsius. if they wont come loose then it will become breaking the bolts.
 
If the bolts are long, chances are you will break the heads off and the rest of the bolt will be stuck in the intermediate housing. The way I get the bolts loose is with a heavy arc welding rod and a good heavy set of jumper cables and a 4d battery with a full charge. Ground the battery to the engine and put the weld rod in the other lead and hook it to the positive of the battery. Now touch the rod to the head of the bolt you want to loosen hold it there until the rod starts to smoke. (This will heat the bolt all the way to the threads and loosen the corrosion that is holding it tight.) Put a socket on it and start to loosen it.

This is not an easy thing to do, but it works.
 
Most power head attaching bolts are not rusted in place at the threads. The aluminum housing that the bolts pass through corrodes and synches around the shaft of the bolt. Usually the whole length of the bolt.
 
Thanks for all the advice guys. I'm happy to say that I now have 8 loose bolts. 5 are out and 3 are nearly out.

I applied the 50/50 mix of ATF & acetone where I could get to the threads and let it soak in overnight then heated the bolts with the welding rod connected to the battery trick.

It took a few goes with the welding rod to loosen some of the bolts (each time they moved a little) but it works a treat.

Nothing broken (yet)

I was considering the recycling yard before I found this forum, so i appreciate all the advice provided.

Bestfishes
Craig
 
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