Lubricating stainless steel threads.

[Freeman22]

I have finally managed to get the gearbox on my 40+ apart, but only after using a blow-torch on all the screws. I am replacing the screws with nice shiny stainless Allen-headed ones from Jon, but I wonder whether I should be using a lubricant on the threads (as I think you're supposed to with stainless), so I can undo them in the future if I need to. When I was working on bikes, we used a copper-based grease, but on a Seagull used in brackish water, I think there might be a galvanic reaction which destroys the aluminium gear-case. Any materials scientists got an idea? Copper grease, ordinary grease, nothing at all, or should I just use thread-lock?

James

[1charan]

O boy, you are making it more difficult for yourself.

If you look at wikipedia, search for Galvanic Series. You will find that aluminium (gearbox) is close to steel, in other words, there is not much electricity between them. Stainless Steel and aluminium are far apart, so this is a very corrosive situation. To prevent the auminium from being eaten up, you would need something even further down the scale, i.e. a zinc anode.

Personally I would not do this in salt water. In fresh water I would use stainless steel bolts with copper grease or actually anything that keeps the water out and the thread protected. If you do not like the color of copper grease, there is also a silver coloured grease.

[Lahtinen]

I've seen aluminium grease (for car brakes), I suppose that's the silver colored one which 1charan mentioned. I think that would be safe choice

[Stelios_Rjk]

I could imagine that there should be another stuff for that purpose that "dries" after a while. I use the silver/gray stuff (anti seize compound) from permatex that contains graphite. It does great job but I remember once, some bolts came off. For example, no way such stuff should be used on head bolts. But over there there was something used. What could that be? Any ideas?

[Shearwater]

What about Ceramic grease? I use that for the brakes of my car instead of copper grease. Ceramic grease has the advantage that it is very well water resistant, doesn't dry to a crust and doesn't affect any metals. It has a white colour. I was considering to use that on the bolts of my Seagulls to prevent them from getting stuck in corrosion. Good idea?

[Lahtinen]

---It does great job but I remember once, some bolts came off.---

I thought that too, just after my posting. Maybe lock washers? Or threadlock (Loctite etc.) just under the bolt head?

[Stelios_Rjk]

Yes but locktite can't be combined with RTV. RTV should be tightened even one day after applying. I use Hylomar on the leg screws. It's a non setting gasket material.
But I still can't locate the correct stuff as used on head bolts.

[Gannet]

I would take a simple approach by using waterproof grease in conjunction with the original type carbon steel plated bolts.

I don't know whether BS used any grease during the original assembly. The lack of which might explain the difficulty in disassembly. However, there is also the corrosion over 30+ years. Perhaps waterproof grease will make it easy to remove the bolt in 30 years time!
My personal view is that socket head cap screws don't look right on an old Seagull, although they do have advantages.
Jeremy

[headdownarseup]

my view on this with regard to the lower leg unit (which will spend a lot of time IN the water) is not to use stainless bolts and nuts but the originals in conjunction with a good quality waterproof grease of some kind. (and dont be shy with the grease, more is better) any surplus can be wiped off on completion.
from the mounting bracket upwards, there's nothing stopping you using stainless nuts and bolts in the powerhead (i would also use something like hylomar or rtv to seal the crankcase, but for example on a 102 with the tank mounts which are drilled into cast iron, i would use a copper grease/anti seize grease that is fairly heat resistant)
if the nuts/bolts etc come into contact with heat (as in the power head) caution must be used. the grease will eventually dry out.
the corrosion usually is more on the outside of the motor (nuts, washers, split pins etc) this is where you can substitue the originals for stainless steel. (they look nice as well but can be costly)

whenever i am rebuilding a motor, i am always thinking about the next time the engine has to come apart. a little dab of grease here and there will help in the long run. it just makes things a lot easier the next time you undo anything.

jon

[RickUK]

Apart from the lubrication ( I use copper grease for reassembly), run a tap down the thread to clean out the 'concretion', and a die on male threads, but a wire brush will do the latter if a die isn't available.
Being a bit odd, I normally do female threads 'uphill' so the debris drops out as the tap goes in then out, but an airline will do the same job.

Run the fastener in and out before reassembly, just to make sure it runs in and our freely.

[Vic]

Tef-Gel

http://www.tefgel.com/contain.php?param=tefgel_infor

[fleetingcontact]

Tef-Gel looks like a good compound except it seems to be intended for anything which doesn't get hot - at least there is no specific statement by the manufacturer that it is intended for use with engines.

The yanks are keen on something called 'Jet-Lube Anti-Sieze Marine Grade' which has a stated upper temperature limit of...lots. More than a Seagull could generate. And it's based on molybdenum so no worries concerning bad reactions with salt/copper/aluminium/steel, stainless or otherwise. Used by offshore exploration companies...