Seized hex bolt in Volvo 120 saildrive prop

[bluedragon]

The hated hex (Allen key) bolt which passes through the cone and prop on my Volvo 120 saildrive refuses to budge this year! The hex socket is getting worn with all the tries and it's now hard to get a grip even with a hex tool which I normally use on a 1/2" socket handle. I'm not sure where it's stuck, but suspect it's corrosion or anode decay residue where it passes through the cone. I put a touch of Loctite on the thread last season, but that's always released OK in the past.

I've tried moderate heat and WD40 today, and pressing hard into the hex socket, also a few hits from an impact driver. No sign of movement. I'm beginning to think I'll have to drill out the cap head (should be fun with a hard S/S bolt) and then the cone should just spin off as usual.

Any other thoughts or bright ideas??

 

[MoodySabre]

You can buy extractors (google will find you loads) but I'd start by borrowing one from a friendly car mechanic.

If you drill the head off (slowly and lubricated) then you still have the rest of it to get out.

 

[Tranona]

It will come eventually. Squirt penetrating oil in and leave it. Wedge the prop against the hull with a block of wood before putting leverage on the bolt. Replace with a new one and loctite every time.

 

[savageseadog]

Boiling water from a kettle is the most safe and effective way of heating it if you didn't already know

 

[PabloPicasso]

Replace with new That seems to be standard practise. Is it the annode bolts? New bolts have always been provided with new anodes even with non-Volvo after market replacements. Why would you put the old ones back?

Which loctite did you use? Blue releases when pressure applied by a spanner key/socket, heat (think blow torch) needs to be applied to red as well as a spanner/key/socket, and epoxy type loctite will NEVER be undone. Let's hope you didn't use this last type by mistake hey!

 

[rogerstown]

Drilling out the cap is not difficult, use a new or at least a resharpened 8 m/m drill, slow speed and WD40 to cool and lub. The cap will come off allowing the cone to be removed and leaving enough of the screw to be gripped by a vice grips or better still small stilson pipe wrench. Having to do this job ever year I bought a bag of 50 of the cap head bolts. Now I put a new bolt in every year and I don't have to drill so often.

 

[bluedragon]

Drilling out the cap is not difficult, use a new or at least a resharpened 8 m/m drill, slow speed and WD40 to cool and lub. The cap will come off allowing the cone to be removed and leaving enough of the screw to be gripped by a vice grips or better still small stilson pipe wrench. Having to do this job ever year I bought a bag of 50 of the cap head bolts. Now I put a new bolt in every year and I don't have to drill so often.

Thanks, that's exactly the procedure I'm thinking of. It sounds like it did the job for you. I'll certainly be using new bolts from now on, and coating the shaft that goes through the cone with grease or similar (I did that the first year after I bought the boat, but then got a bit complacent).

Just to answer a few of the questions raised by others:

It's not the anode screws, but the long machine screw that runs from the front of the cone to the drive shaft (stops the cone unscrewing). Once the cone is off, then there will be enough screw shaft exposed to get a good purchase on it.

It was red Loctite, but it's released OK in previous years. I should get some blue, I know.

I've thought about a stud extractor, but not sure it would take the load of breaking-out the bolt.

 

[rogerstown]

It was red Loctite, but it's released OK in previous years. I should get some blue, I know.

I've thought about a stud extractor, but not sure it would take the load of breaking-out the bolt.

I always use red Loctite (three digit number which I can't remember now). A fiend's s/drive prop fell off in entrance to Strangford Lough where tide runs at up to eight knots, so I like my prop good and tight and the red will undo.
Even if the bolt sheared of flush with the prop shaft you could still drill it out and re tap the internal screw on the shaft. Breaking a stud extractor could leave a rock hard piece of extractor that would be nearly impossible to drill out, and very expensive to fix. Best not to push smaller sized extractors to hard.

 

[bluedragon]

In the end a friendly engineer with an oversize 1/4" allen key and big hammer managed managed to cut a good enough purchase in the head to get it out. Last option before drilling he said. It worked.

 

[nigelmercier]

Glad you got it sorted. I never use Allen keys any more, the 1/4" drive type is much better: http://amzn.to/1i9gMC9