outboard clamp - preventing thread spalling

[skyflyer]

I think thread spalling is what I have - when I removed outboard from transom mount at end of last season I noticed the threads were very stiff. The threads are stainless steel, obviously, and the material of the clamp is some sort of alloy casting.

I have managed to free them up by backing-off and winding-on alternately using ordinary grease to lubricate but what can I use to stop this happening again or getting worse. I have some Duralac but that sort of sets so isn't appropriate for a thread that is in 'regular' use. Tef-Gel maybe?

 

[PetiteFleur]

I just make sure they are kept well lubricated - but I only have a 2.2hp Suzuki which is used regularly.

 

[PlankWalker]

Just keep the threads and other external moving parts well greased, definitely don't use Duralac.

Plank

 

[VicS]

I think thread spalling is what I have - when I removed outboard from transom mount at end of last season I noticed the threads were very stiff. The threads are stainless steel, obviously, and the material of the clamp is some sort of alloy casting.

I have managed to free them up by backing-off and winding-on alternately using ordinary grease to lubricate but what can I use to stop this happening again or getting worse. I have some Duralac but that sort of sets so isn't appropriate for a thread that is in 'regular' use. Tef-Gel maybe?

Galling is what its called but simply corrosion of aluminum in contact with stainless steel produces such a large volume of oxide that that alone will cause stainless steel in aluminium to seize up solid.

My 'rude is 30 years old. I grease the threads every year, along with all the other lubrication points listed in the maintenance schedule. No bother as a result even though I use some water proof grease I "acquired" years ago rather than the specified OMC triple guard


Remember that stainless steel in stainless steel can gall ....as in rigging screws!

 

[ghostlymoron]

I was told by our metallurgy adviser some years ago that any product containing lanolin is a good preventer of stainless galling. We used Boots hand cream on site after that.

 

[macd]

I was told by our metallurgy adviser some years ago that any product containing lanolin is a good preventer of stainless galling. We used Boots hand cream on site after that.

+1 for lanolin between stainless and aluminium (where the parts are routinely moved). 'Pure' lanolin can be bought quite cheaply from chemists and is quite viscous at typical UK temperatures. Alternatively, cadge some from anyone who's tried (and failed) to antifoul their prop with the stuff

 

[Lon nan Gruagach]

I was told by our metallurgy adviser some years ago that any product containing lanolin is a good preventer of stainless galling. We used Boots hand cream on site after that.

Interesting.. I guess its going to be easier to take the bolts to the sheep rather than the sheep to the outboard or outboard to the sheep..
Island thinking....

 

[lw395]

I find an anti-seize grease like 'Nevr Seize' works well.
It's a balance between lubrication and mess that gets everywhere when you move the outboard around.

 

[ghostlymoron]

Our metallurgist said that it doesn't have to be pure lanolin, anything containing it would do. Hence the hand cream!

 

[DannyB]

Our local fabricator recommended milk of magnesia on stainless steel threads to prevent them seizing, I'm not sure if that contains lanolin.

 

[lw395]

Our metallurgist said that it doesn't have to be pure lanolin, anything containing it would do. Hence the hand cream!

Which will contain water, promoting corrosion?

 

[VicS]

I dont know why the answers to a simple question become so complex

Just grease the threads,
If the owners manual has no other recommendations just use the same grease as for other for external lubrication points requiring grease.

 

[johnalison]

I never have this problems with outboards because greasing the threads seems such an obvious maintenance measure, but I did encounter it on a mainsail track fitting that needed removal. When I whinged to the maker, Lewmar, at a boat show, his response was "don't you dismantle all your S/S-Al fittings each year and use the recommended grease?". Apparently, it is in the instructions for such fittings, including genoa cars.

 

[Spyro]

Happened to mine as well. I had to tap out the thread then applied grease to it, it's been okay for few years now

 

[Lon nan Gruagach]

his response was "don't you dismantle all your S/S-Al fittings each year and use the recommended grease?". Apparently, it is in the instructions for such fittings, including genoa cars.

Having recently worked on a 15m aloominum boat my answer to him would have been quite a bit of stammering and choking. Hopefully finishing with "No, it would be nice to sail for more than a day per year."

 

[macd]

I never have this problems with outboards because greasing the threads seems such an obvious maintenance measure, but I did encounter it on a mainsail track fitting that needed removal. When I whinged to the maker, Lewmar, at a boat show, his response was "don't you dismantle all your S/S-Al fittings each year and use the recommended grease?". Apparently, it is in the instructions for such fittings, including genoa cars.

The major (i.e. larger) fittings on my Selden/Kemp spars are into thread inserts, which are stainless. I've no idea of the grade, but this means any dissimilar metal corrosion takes place between the thread and the aluminium, rather than between thread and fastener, which I consider a far superior arrangement. Since I have a range of inserts handy from a previous existance, I've no hesitation about using them in places which might otherwise be problematic. Outboard friction clamp bolts are one; the silly grub screws below the furling drums are another. The manufacturer of the latter also recommends annual disassembly and greasing, which is just another way of making the problem mine rather than his.