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The upper nut on the forward, outboard engine mount on my port engine is frozen. The previous owner's mechanic did not tighten it when he installed the long blocks, so the engine alignment is being held by the bottom nut, gravity, and the remaining three motor mounts. Apparently, it is not causing an immediate problem because people at the yard said my alignment was good after I replaced my stuffing box hoses and installed new split couplings last year. I have not noticed and vibrations since then. Given the location, getting decent leverage is difficult and I am concerned about throwing the alignment off in the process of loosening the nut.

I have been soaking it with Corrosion-x and PBblaster since last summer without much luck. I haven't been able to find a nut splitter large enough to split the nut.

Any suggestions?

If CX and PB blaster isn't working, apply heat to nut with a concentrated flame. One of those butane crack torches work good, use it all the time at work.
If the nut and the stud are fairly clean of rust, then the threads may be galled. If thats the case then use an impact, air or battery, to try and loosen.

If you use heat, also take a piece of wax and melt it into the threads. The heat helps t pull it into the threads. I use a piece toilet bowl ring. A candle will also work. Also if you heat it you can quench it with water to make the nut contract quickly and compress any corrosion. If you can put force on it with a breaker bar, have someone tap it with a hammer while holding torque on it. Here is a good way to accomplish the same thing if you have air and a air hammer available. Amazon sells them. Great for manifold bolts too!

https://mayhew.com/product/model-37316- ... pneumatic/

Can you tell I work on old rust equipment much!!! LOL

Rawleigh

Is it safe to assume the wax is for lubrication? I have never seen that trick before.

I like that tool Rawleigh! I see one in my toolbox soon, thanks.


What I have in my toolbox that has saved many a day is this manual impact tool. Works great, especially on screws were the screwdriver wants to slip out as you apply force. This has the bit rotating with shock as your hitting down driving the bit down keeping it seated.


https://www.tooldiscounter.com/product/ ... b83e35f106

If you can’t get anywhere with all the above techniques (I’d try heat first), there is a tech at work that has one of these NOT made in China splitters. Double edge, and let me tell you, the steel is real hardened steel unlike crap of other ones!
Good luck and be careful.

https://www.mscdirect.com/product/details/94541463

I am assuming that the motor mount is now bad and needs to be replaced

all the solutions above are probably the right way to go about it but there is another shade-tree less elegant method, take some pressure off the 1/4 of the engine with the bad mount by jamming a piece of wood to support the motor when that mount is temporarily not there then use a saws-all to cut the bolt just under the engine side of the mount plate that way the top part of the bolt with the nut can be lifted up, the motor mount unbolted from the stringers then replaced.

$4-5 for a decent metal cutting sawsall blade, $80 for a new motor mount. @10min to cut the bolt
https://www.ebay.com/itm/140973145389?e ... XQySpRN1zh

Tony: Yes, the wax wicks down into the thread with capillary action and helps loosen it.

Nice trick. Thanks

That Kukko nut splitter is a beautiful piece of kit.
Expensive, but looks like it would easily do the trick

Try a mix of transmission fluid and MEK. If none of the ideas above doesn't get out the cutoff tool.

Bees Wax, melt wax over stud so that it flows over nut and down threads. We used it regularly for 30 years on the steam ships I sailed on. Always had a block in the Machine Shop. Best natural penetrant I ever used. Tap flats on nut in addition. Good Luck. EarleyBird

To follow up Earley Bird with a steamship trick learned from a first engineer a long time ago:
-Try a cold chisel on the flats of the nut, will make the threaded holes slightly larger, the nut is now junk, but the part is loose.

A more modern trick: I keep a squeeze bottle of half acetone and 10wt oil in the tool bag. Shake and apply liberally to offending part. The acetone drags the 10 wt into the threads and evaporates, works REALLY good on SS in aluminum. DO not apply heat for a bit, as bad things happen with fire and acetone

I am not going to go into creamy peanut butter and a heating pad, but that can work as well.

Good luck with it.
Pete

Thanks for all of the suggestions.

I ended up making three cuts in the nut with the a cutoff disk on a Dremel tool. I was able to slip a screwdriver blade into one of the slots and break off a chunk of the nut. The remaining part came off easily with a box wrench.

Sweet! That works! How did the threads survive?

After I used the c-shaped remnant of the old nut as a die to clean up the threads, the new nut went on easily.