how to loosen BIG nuts?

[mlydon]

There are additional nuts Underneath the tranny foot, which allow you to adjust the trans height (usually two, lower a stop nut for the upper) Get a wrench on the bottommost one, another on the top, and use a lever to force the two wrenches apart in the right direction, turning either nut away from the foot..

And as I suggested cutting with an ange grinder before, you could cut UNDER the foot. You could also remove the bolts attaching the mount to the bed, or the foot to the engine, and get them off the motor after you’ve moved the motor.

Matt

[Hermia II]

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 beg to disagree. Rubber can take about 180°C so you can heat the nut quite a bit (not glowing orange/white of course), and you have the engine foot as a cooling flange. Just so that it expands a bit and breaks the corrosion bond.

[skipmac]

Originally Posted by Compass790

I wouldnt describe them as big nuts but an impact wrench ( aka rattle gun) will make short work of them especially if you spray them with penetrating oil & leave overnight before hitting with a rattle gun.

Absolutely try an impact wrench. I had a 2" nut that resisted all attempts over three days starting with a 3/4" drive socket wrench, repeated soakings with PB Blaster and finally a 2' breaker bar with a 2 1/2" pipe for extension.

Finally tried a battery powered impact wrench and it popped off in two seconds.

[peterincalgary]

Years ago, working on a BP tanker in Camel Lairds Birkenhead we were working on the deck lines, couldnt move the nuts, when I asked the foreman, who was Irish, said in his brough "can you cut it" which was a big hammer & chisel to crack the not, it worked.

[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

[DesKeech]

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?

Get a gas bottle and get some heat on them, it'll melt the nyloc you'd probably want to fit new nuts anyway.

[Rumrace]

Touch of heat then penetrating oil and a power bar

[sailingchiro]

I use a breaker bar and pipe over the handle to extend leverage. I would probably order new motor mounts prior to work just in case the rubber mount breaks loose or bolt breaks.

I would definitely spray some penetrating fluid on your big nuts prior to removal.

[longjonsilver]

Worlds best penetrating oil is also the cheapest.

https://www.youtube.com/watch?v=o7hpmmlYBFM

Ask me how i know.

[vanderd]

I just changed all 4 mounts on both engines. In a couple of cases it was easier to unbolt the mount from the engine and put it in a vise. It also gives you a lot more room to swing wrenches and possibly avoid the need for an extension. Plus if you need heat it’s a-lot safer off of the boat

[Boatyarddog]

Originally Posted by Compass790

I wouldnt describe them as big nuts but an impact wrench ( aka rattle gun) will make short work of them especially if you spray them with penetrating oil & leave overnight before hitting with a rattle gun.

Rattle guns and SS nuts is NOT a good idea, galling happens then it's not coming off.
Get it red hot!
Pretty safe spot for that, that mount is toast too!
Or slice it with a cutoff tool or dremmel and cut off disc.
Boatyarddog

[garyfdl]

In 50 years of wrenching on stuff, I've never found that a propane torch could put enough heat into a stuck fastener, unless it was very small. And given that it appears the nut is on a elastomer vibration mount, I'd stay away from heat altogether.

A pneumatic impact (rattle) gun is also not a very good choice (IMO) unless you have a virtually unlimited air supply. The typical 'household' compressors can't put out enough volume at pressure to be effective.

So? I'm in the penetrating oil/electric impact camp. I use Kroil Oil, but PB Blaster, and 'weasel piss' (atf and acetone) work well too. Just be aware the acetone is aggressive towards a lot of plastic compounds and might dissolve them if left to 'soak'.

Good luck!

[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.

[AKA-None]

Ideally if you need heat the you want hot a fine control
Eg acetylene and a small tip to heat the nut only then work fast and do not stop turning until it’s off
Once the bolt gets hot you’re done

Otherwise use a nut splitter

[sazarac]

Unbolt the mounts from the stringers.