Yanmar 4LHA htp replacement

[blunted]

The alt attaches to the bracket with a long bolt. Yours has broken off the threaded end. The 'sleeve/insert' you can see in the aft alt tang is to allow for slight differences in the spacers andengine mounts. It is meant to slide towards/into the alt arm to take out any gap in the installation. It is common to tap this sleeve out a bit prior to installation of a alt to get enuff gap to easily install the fiddly spacers. A new alt comes with the sleeve un-installed. The forward alt arm does not have this sleeve.
Removal - I'd concentrate on applying rotation, the alt arm is just cast aluminum. I suspect the bolt failed at the start of thread & still goes almost all the way thru the system. Stick a probe in the hole & measure depth.

Thanks Zonk and Longy,

The mystery is: how is this thing still welded on so tight? I can barely rotate the alternator itself, the bolt is seemingly welded to the alternator tab. All this with no nut on the back to hold tension.

What is it, that this bolt is threaded into that's gripping so perfectly.

Back to the boat on Sunday morning to find out, I hope

 

[longy]

Rust never sleeps. Take the belt & tensioning bracket off. Try to get the alt rotating on the mount. Usually you can get a thick piece of wood into the gap for leverage. LOTS of penetrating oil! Bolt only threads into missing nut.

 

[blunted]

Rust never sleeps. Take the belt & tensioning bracket off. Try to get the alt rotating on the mount. Usually you can get a thick piece of wood into the gap for leverage. LOTS of penetrating oil! Bolt only threads into missing nut.

Oh yes that's exactly what I am talking about the alternator is not even moving. This is where I started the whole process, taking off the belt etc, before heat, lube, foul language etc.

• No belt
• 3' long metal rod for leverage
• I have even taken the fresh water pump off the front of the engine to give me better leverage
• And I can still barely budge the alternator itself, much less that damn bolt.

Thank you all for the input

 

[longy]

Welcome to the joys of boat ownership!
When all else fails (or you get really mad): Cut off securing bolt about 1" behind the mounting ear on the engine. Remove all the bits of spacers. Flood with penetrating oil. Make alt move. Cut off head of bolt. Remove alt. Now you've just got frozen bolt in engine block ear with stubs out both ends. Apply heat, oil, large vise grips, copious amounts a swear words. Have a beer. Repeat as needed

 

[blunted]

Welcome to the joys of boat ownership!
When all else fails (or you get really mad): Cut off securing bolt about 1" behind the mounting ear on the engine. Remove all the bits of spacers. Flood with penetrating oil. Make alt move. Cut off head of bolt. Remove alt. Now you've just got frozen bolt in engine block ear with stubs out both ends. Apply heat, oil, large vise grips, copious amounts a swear words. Have a beer. Repeat as needed

I'm being supremely patient with this one, under normal circumstances I would have had it that fucker off with a sawzall weeks ago, but I need the block intact.
And everyone here knows, I more of a weed guy

 

[Zonker]

I'm guessing frozen into the alum alternator housing. Get a big breaker bar on the nut. SOMETHING will break (probably the head of the bolt). Then drill out the bolt

 

[DDW]

Oxy acetylene cutting torch. I knew a guy that could do this. Heat the bolt to bright glowing red, then hit the oxygen lever. The steel burns out while the aluminum and iron will not. I watched him burn a broken stub out of an engine block, 2" of buried stud vaporized and the threads in the iron block were perfect. Took about 15 seconds.

You may want to practice on some scrap first.....

 

[blunted]

Had I the skillset, I would have welded a large diameter nut to the end of the bolt by now for bigly leverage

 

[longy]

Strange factoid: the stock Yanny bolt is NOT a tight fit thru the various holes. I don't remember just why at the moment, could be threads were rolled on (in?)

 

[blunted]

Well, shit got Medieval on the bolt.

I didn't need a spare alternator anyhow. You can see the bolt was broken off part way through the threaded bushing / long nut.

I got the nut up to 800F, nothing
Filing the bolt straight, nope
pipe wrench, nope
Eventually I caved and cut the alternator off the front and the back came right off as the back tab was not actually fastened to anything,

I then was cutting the nut next to the block and I took another shot of heat and pipe wrench on the back to finally get it moving. Eventually I managed to unwind the nut from the bolt.
To answer my original question, no, the block is not threaded.

 

[longy]

That was a very non-standard install. That bolt never went thru to the back of the mounting, the back ear of the alt was completely unsupported.