how to loosen BIG nuts?

[s/v michaela]

And if all else fails use a nut splitter ....

[Bent Bugle]

Originally Posted by billgewater

How to remove big nuts? In Australia we do that by voting.

Yeah but which big nut do you vote out....getting back on topic I'd go the PB blaster overnight & socket with extension on the handle before ( whilst holding back on the mount to stop twist)I did anything else...

[Compass790]

Originally Posted by Bad Sailor

I had the same problem with my big nuts. My issue was that the torque I applied to the nut was absorbed by twisting the rubber in the mount. The nut was screwed to a stud that was welded to a metal plate that was bonded to the rubber. I had to stop the twist by restraining the metal plate with mole grips or an adjustable spanner, wedged up against something firm. Then, using a breaker bar, all the torque was transferred to the nut and hay presto! In my experience on automobiles, using a rattle gun on parts that are bonded into rubber/plastic mouldings, just shears the bond with the moulding, rather than loosening the nut. Good luck!.

Ah yes you raise an important point there. I did not think thru the effect of the rattle gun on the mount. Would be better to split the nuts if he wants to save the mount

[Boatyarddog]

Originally Posted by stormalong

If your engine mounts are more than ten years old now is a good time to replace them. Did mine at 18 years and it was quite a job reaching the aft ones.

I am in the heat and breaker bar camp.

Hardcore.
Those mounts really are ugly.
Just slice the nut right up next to the bolt it's fastened to, then a chisel to the edge will loosen it right up.
You'll barely touch the bolt threads.

Boatyarddog

[Celestialsailor]

Originally Posted by Hermia II

If you want to avoid too much brutality, start by heating the nut from the side with a propane/buthane flame Ø 10 - 15 mm so that it gets really hot. If you after that can not just use a wrench, then the rattle gun will fix it easily.

It takes very little heat to get the nut to expand a little bit and loosen. I am a Toolmaker and have had to deal with these situations for many years. However, a propane torch does not produce a large amount of heat and if done correctly...Heat, penetrating oil, heat, penetrating oil. Let set for a few hours, then heat again, an air or electric 1/2" impact driver should rattle it right off.

Originally Posted by Martkimwat

Certainly would NOT do that, as it will damage the rubber mount below it and probably render them useless. Knowing how much some engine mounts can be to replace, I would do my best to not damage them unless they are already beyond redemption. There is also the very real risk of igniting the rubber with attendant toxic fumes and fire risk.

I would agree if it was an Oxy/Ace torches. Although I have used a small brazing tip to concentrate the heat on said nut. But the method described to Hermia works as the nut is a large mass and absorbs a lot of heat. I suppose if there was concern, a wet cloth, on the rubber, could keep things cooler.
Both Urethane and natural rubber can withstand about 250F, I believe.

[seabreez]

Originally Posted by SteelCruiser

wanting to remove my gearbox
thus, trying to lift my engine ‘up 6 inches’ and ‘forward 6 inches’

Lister STW 3. LH150 gearbox - burnt out clutch

struggling to loosen the 4 x 15/16th nuts
Attachment 256728
any suggestions?

Use a nut splitter... really is a great solution on boats. Check this link

https://www.amazon.ca/Splitter-Damag...8HSX4JRS&psc=1

[JC Reefer]

How to loosen BIG nuts?

Heat is your friend. I start by warning my hands a bit. Rubbing them together and blowing some hot breadth through them.

The main this to avoid them getting cold. If you let a cool draft blow over, or dunk them into cold water then those nuts will tighten up real quick.

Metal shrinks…

[wingless]

Originally Posted by SteelCruiser

wanting to remove my gearbox
thus, trying to lift my engine ‘up 6 inches’ and ‘forward 6 inches’

Lister STW 3. LH150 gearbox - burnt out clutch

struggling to loosen the 4 x 15/16th nuts

any suggestions?

Thanks for saving a kiloword by providing an image.

A correctly-sized (previously specified 15/16" or a 24mm) ½" drive six point DEEP socket, instead of the normal depth 3/8" drive socket shown in the image will work w/ the "boxed-in" clearances for the top nut shown in the image. A correctly-sized combination wrench (open end one side / box end other side) is the correct tool for adjusting the not shown nut on the bottom of that motor mount.

It will be LOTS easier if using a jack or a lever instead of the bottom motor mount nut to unload the mass before raising.

Note for raising that mount, the notched clearance on that side support is already at the end of it's range.

An ideal tool to increase the cut in that side support is an Oscillating Multi Tool (OMT) w/ the appropriate sharp blade. Note that it is easy for an OMT cut to go awry so maintain control and observation during the cut to abort / reset if required. I would not go the full cut depth already shown and instead only cut a little more than is required.

If moving "forward" is down in the image, then using an appropriate thickness spacer will be handy when sliding the mount past the edge of the existing block shown in the image.

Showing once again my firm grasp of the obvious, the motor mount nut shaft does not have the previously specified 6" of lift remaining in the adjustment range, probably about ½" of UP remaining, so spacer blocks are already required.

Frequently supporting the combination engine / transmission mass is shared by mounts on each component, so when detaching the transmission from the engine ensure that sufficient support is provided at the (previous) middle on each part.

[ChrisJHC]

Originally Posted by longjonsilver

Worlds best penetrating oil is also the cheapest.

Ask me how i know.

I like the fact that his “secret ingredient” is a small amount of a good Scotch.

I find that sufficient quantities of Scotch mean that I no longer care about getting the nut off!

[SteelCruiser]

Thanks for all the suggestions
.
My ignorance shows : What do I replace the engine mount ‘stuff’ with
The old /current stuff is all crumbling away
.
see pic

[Toccata]

Looks like a "Polyflex" mount to me
Unfortunately the corroded areas are steel components

[GILow]

Originally Posted by RaymondR

Drill down vertically on both sides of the nut with an electric drill then split the nut with a cold chisel. That way you will salvage the engine mount and only need to replace the split nuts.

This. A great approach. Done it more often than I care to remember.

[GILow]

Originally Posted by billgewater

How to remove big nuts? In Australia we do that by voting.

No, we vote to change nuts.

[GILow]

Originally Posted by mlydon

looking down from the top, you put one box wrench on the lower nut, below the foot, so that the wrench is at 6 o'clock. position the other wrench on the upper nut so that it's also at 6 o'clock (or in the neighborhood).



now, looking from the 6 o'clock side, you have two wrenchs pointed at you, one a few inches above the other.



you put a bar, length of wood, hammer handle, whatever, vertically between the wrench ends, so that the bar is on the left side of the upper wrench, and the right side of the lower wrench.



by forcing the bar towards the right from the top, you're driving the upper wrench to loosen the upper nut and the lower wrench the lower nut, using the leverage of the bar, which can be considerable.



I hope my description was somewhat clear. I just took a picture to illustrate the concept.....



Matt

Clever.

[dkenny64]

old mechanics trick.. heat the stud/nut.. then melt wax in the threads..
might take 2 or 3 tries..
beyond that are you trying to save the nut of the stud. cut the nut vertically. then wedge it apart.
-dkenny64