What is the Name of the Tool to Remove this Nut?

[dick sargent]

Can't see in photo, but are you sure the nut and pulley aren't one piece?

[BrianGJS]

Although not addressing the tool required for the nut in question I have removed a number of stubborn fasteners with a 'trick' a local race engine mechanic shared,
Heat the parts in question and once hot melt paraffin wax (candle will do) into the joint you are trying to defeat. LEAVE IT FOR 15 MINUTES! I have seen very stubborn fastens of dissimilar materials and others just twist off as if they were new.

[ValiantV]

Originally Posted by dick sargent

Can't see in photo, but are you sure the nut and pulley aren't one piece?

That was my assessment as well. OP says no...

[Cadence]

Originally Posted by motion30

My question is why does yanmar or need to use a Fastener like that. It looks like they tried to make it hard poor service the more I see of them the less I like yanmar

I'm wondering if it isn't made to accept some sort of accessory. What I haven't the slightest. It does not seem likely it is machined to make it difficult? If so they did a good job of it.

I might try fabricating a tool from a piece of pipe with a torch or welder to produce the flats. Or possibly putting a bend in an open end wrench near the head. I have one around someplace and can't recall what I sacrificed the wrench for. I think a bastard crankshaft nut. A bar can go through the other end for leverage.

[skipgundlach]

Note also that the lines of the flats are not parallel; there's a small taper.

I have the same shape on the shaft of my KISS wind generator; there's no mechanical reason I can see for that, but there it is.

So whatever you build will have to be asymmetrical to be best...

[guyrj33]

I believe the intended tool to remove the pulley is an open end wrench.

[Matsubob]

Yes, that is a strange one! I normally refuse to use crescent wrenches or vise grips on engines, but in this case, I used a pair of vice grips, at an angle because of the inset. This is the alternator drive pulley that fits on the "crankshaft". This shaft is really an extension of the crankshaft, so comes off with the front engine cover.
I first sprayed WD40 on the threads (RH, definitely) and then gave the vise grips a good couple of whacks with a hammer and it released and spun off.
There may be a special Yanmar tool but no standard shaped socket will fit on that strange nut. I considered installing a normal hex but decided to just use the original.

[Bleemus]

[Kosarchuk]

You didn't provide dimensions, but you might try a large 8 point socket with a pair of shims to "fill" the space adjacent to the flats. If it's really large search for sockets for "frog" bolts.
The other comments about this possibly being one piece may be valid too........I didn't not see a clear indication of it being 2 piece either.

[hellosailor]

Wotname-
Being as the but is in a "cup" already...Fill the cup with a slush of broken up dry ice (if locally available, often in supermarkets?) and alcohol. Let it ice down the nut solidly. Then remove, heat up as much as you feel safe with (cautions on the alcohol fumes as well as the dry ice) and repeat the cycle 3x. Guaranteed that whatever tool you chose, that bolt will come off without a lot of argument.
The only big question being whether you have a local dry ice source. Supermarket, ice cream or frozen food shop, sometimes industrial sources. I think it is about $1/pound here, and ten bucks worth would more than cover what you need.

[ebisucapt]

What about trying a strap wrench and go on the outside of he pulley?

?

[Cadence]

Originally Posted by ebisucapt

What about trying a strap wrench and go on the outside of he pulley?

?

I would give dollar to donuts the pulley is keyed.

[kelbylinn]

That nut reminds me of the water meter off and on valve. not sure on size of nut, but these types of water meter wrenches are readily available at Lowes for example...

https://www.google.com/search?q=wate...RyirpAcmzptlM:

[farmall.dude]

Lots of great ideas, but I don't see where anyone mentioned PB-Blaster. Someone mentioned restoring old tractors, which I tinker with, and I find this stuff to be amazing. Squirt a little on the threads, wait a minute or two and generally nuts that have been rusted on for 60+ years spin off without too much effort.
The Dry Ice idea was my next thought, but instead of trying to hunt down dry ice and potentially getting a thermal injury, go to the local big box technology store, or office supply store and buy a few cans of the stuff used to blow dust and debris out of keyboards and electronics. Turn the can UPSIDE DOWN and aim the tube at the center of the stud and squirt. It will quickly freeze the stud, theoretically shrinking it hopefully enough to break the bond. Wear gloves because the can gets mighty cold too. You can spray PB Blaster then canned air a few times. It may be enough for the PB to seep in far enough to free it.
But, it seems like you asked for the name of the tool, not advice on freeing a stuck nut! I don't have a clue for that, but I'm thinking an offset open-end wrench is what you need. You say there's a slight taper so it's most likely a specialty tool as you suspect.
Good Luck!

[newhaul]

An odd idea. Check with companies in your area that work on the refer unit on semi trailers. Thermo kings use the yanmar engines.