Okay, not cycling related but will be a challenge.

[widget]

.........to all the technical boffins - and I hasten to add I am not one of them.!

 

Anyway, today I had my outboard engine serviced, its been used in salt and fresh water recently, but I maintain it with its regular servicing.

 

Anyway, the mechanic calls to say he cant get the stainless steel grub screws out that allows him access to the inside, he tells me the screws and the aluminium housing have corroded / welded together and the only remedy is to drill the screws out but this will require a new cover (approx R8000.00) and helicoiling (or something) the block, Labour etc - entire job about 10K.

 

I asked how can this happen and he waffled on about some block that stops corrosion between two metals which is worn out and thats what has happened, the engine is three years old so out of warranty.

 

Anyway, I said hang on, I have to think about this before I say go ahead, because my non technical brain tells me surely something can be done besides drilling.

 

Now my question to all the technical fellas here is -

 

1)Is this possible - the engine is serviced according to manufacturer specs?.

 

2)If the screws are corroded / welded together to the housing is there any way of getting them out besides the suggested method of drilling?

 

I want to use the boat over easter so I need some speedy replies. 

   

[Gumpole]

from a building perspective alu.  and stainless steel are never mixed due to corrosion, so there is usually a seperating tape is used.

in your case maybe there is some other 'sacrificial' anode which will corrode in its place - like in a geyser, so his explanation sounds correct... could be this wasn't replaced in one of the previous services.

 

are you diving in easter?

[bob_the_builder]

it is common practice to fasten aluminium sheets with stainless steel screws

http://www.azom.com/details.asp?ArticleID=1177

 

I think your mechanic is talking out his pooper. Take the boat for a second opinion.

[GreyOwl]

That sounds suspect, I dunno why the normal servicing would not have picked that up?

 

I hope someone can help you...

[Guest Big H]

There is a galvanic action between stainless and aluminium. Why do we put grease on seatposts and bb axles to ensure they can come loose. I have heard of frames that had to be thrown away because the saddle post "froze" in the frame.

 

Widget ensure that the Marine Mechanic does not get away with this. If they did proper services this should not have happened!!!!!!

 

I once had a Contractor that had to cut loose an aluminium bridge railing that "froze" to a steel bridge (the bridge was constructed with Corten steel)

[Johan Bornman]

I don't think the mechanic is at fault. Have a good look at what tasks constitute the type of servicing you have had done and you'll see that testing all bolts and screws for possible corrosion is not on there. One cannot test those things unless the service costs infinitely more, as indeed it does on aircraft.

 

What happened between those two metals is common. Aluminium corrodes and the product thereof (aluminium rust, if you like), is a molecule that's much much bigger than the aluminium atom and therefore it expands and "freezes" anything on close contact with it. It has nothing to do with galvanic corrosion, that alu thread would have corroded with nothing, or any other metal inside.

 

The right course of action is to drill it out and put in a helicoil or similar, as the mechanic explained.

 

What I cannot understand is the cost. I suppose once I see the job I may or may not understand the scope of the problem. I cannot judge whether the cover has to be replaced but I can tell you this, I'll have a damn good go at fixing it before replacing.

 

The only preventative steps I can think of is to manipulate those screws regularly. A grease type substance in there, such as coppaslip or even grease, will form an emulsion and allow the water to stay in contact with the alumium far longer. However, I'm sure the marine industry has a solution or at least, some recommendations.

[lowracer]

what do you mean : not cycling related??????????????

 

EVERYTHING IS CYCLING RELATED!!!!!

 

similiarly to what they say there is nothing new under the sun, or everything is invented allready

 

in google, search for "frozen seatpost" ammonia

 

or just click on the link where I have done it

http://www.google.co.za/search?hl=en&q=%22frozen+seatpost%22+amonia&meta=

 

your options include ammonia, coke, penetrating oil,etc

 

the problem is that alu corrodes and increases in size. ammonia can remove the corrosion

 

lowracer2008-03-11 12:02:18

[gummibear]

When last was it serviced?as this doesnt happen overnight.

Years back when i was a lighty and worked in a bike shop i was tought to put vaseline on all bolts on the bikes and i never had a problem with this on a bike.

Q 20 might work.

[Johan Bornman]

what do you mean : not cycling related??????????????

 

EVERYTHING IS CYCLING RELATED!!!!!

 

similiarly to what they say there is nothing new under the sun' date=' or everything is invented allready

 

in google, search for "frozen seatpost" ammonia

 

or just click on the link where I have done it

http://www.google.co.za/search?hl=en&q=%22frozen+seatpost%22+amonia&meta=

 

your options include ammonia, coke, penetrating oil,etc

 

the problem is that alu corrodes and increases in size. ammonia can remove the corrosion

 

[/quote']

You are right that ammonia can dissolve the white aluminium salt corrosion. However, the solution doesn't lie with ammonia, especially not in a frozen seatpost.

 

Look at it like this: Pretend the corrosion around the seatpost is a thin cylinder of "the stuff" Now remove the cylinder of stuff and put it on your workbench. Now attempt to dissolve it by attacking it with small quantities of ammonia, only on the head-on side of the cyclinder, one small ring, one molecule thick at a time.

 

Had you been able to access the cyclinder from its broadside, no problem, but you can't, the seatpost and seat tube prevents that.

 

Try it, you'll see it doesn't work. I am yet to see a successful ammonia operation on a seatpost or stem.

 

Further, penetrating oil does nothing for alu oxide. It may even make it expand if, and here's the catch, if you can make it penetrate. I've examined seatposts and stems which were frozen, treated with everyting bar coke and brandy, and then drilled/sawn out. There was no evidence of any significant penetration whatsoever.   

 

The ammonia trick is just another cycling myth perpetuated by the Internet.

 

[Johan Bornman]

When last was it serviced?as this doesnt happen overnight.

Years back when i was a lighty and worked in a bike shop i was tought to put vaseline on all bolts on the bikes and i never had a problem with this on a bike.

Q 20 might work.

And then again, Q20 might not work.

 

Actually it wont, but I addressed the reason for that in another post.

 

You were taught only partially right in that bike shop of yours. Whilst it is OK to put Vaseline, or better, copper compound on most nuts and bolts, it is not OK to do so on seatposts and old-fashioned quill stems. These are so-called dynamic joints (it means they still move about inside their fixings) and the movement creates a pumping action that continually pumps water in and out when riding in the rain, after a wash or when seating heavily. Should there be grease in there, you create an emulsion with the water that traps the water molecules for far longer than were it dry. This trapped water then quickly corrodes and freezes the post/stem.

 

If you want to envisage how this pumping action works, think of an old-fashioned quill stem. The expander bolt that holds it in is at the bottom of the stem. Above that is a few inches of unclamped stem that although it fits quite flush into the steerer tube, can still wiggle a little bit sideways even though it is fixed at the bottom. This sideways movement pumps water and mixes the water into the grease.

 

In the case of the boat engine cover, I don't imagine a dynamic joint. However, constant submersion in water is as good and a thread isn't watertight, hence the water penetration and corrosion.

 

The modern threadless stem solved the stem problem neatly, but the seatpost problem still persists. When working on a bicycle, always consider whether the joint is dynamic or static and apply grease likewise. Three suspects are stems, seatposts, pedals.

 

I have no doubt that the boat mechanic has already dried the Q20 trick (for what it is worth). The solution is to drill and re-thread.

 

 

 

 

[widget]

Ai, ai, I stopped off at the workshop last night to see for myself whats going on.

 

Its pretty much as you mention Mr Bornman, somewhere, somehow previously the cover was removed and the little grub screws must have been replaced without the special coating of (blue stuff) that they use, water got into the threads and now they are "corroded vas".!

 

The mechanic said he has been spraying it with everything he can find (WD40, Q20 and some Wynns stuff he showed me) for the whole day but its made no differance.

The problem is these little screws are quite long (about 8mm) and the stuff isnt penetrating down.

 

The issue with the cost is, they dont do the engineering themselves but take the whole engine to a specialist shop to drill and so on.

Apparently the little screws have a head to hold the cover on and when you drill the screw out sometimes the hole gets too big and then the cover wont fasten down, so it has to be replaced, but if they can reuse it obviously they will - as this is the most expensive part. 

 

I just read the bit about ammonia, phoned and asked the mechanic if he knew about it, he said "No" but he will try it if I can get him some and tell him what strength to use (must he dilute it ir not).

 

To be honest he didnt sound very hopefull.

 

So, please Mr Bornman (or anybody else) where do I get this stuff, it dosnt sound like you just go to the local supermarket for it, and how do we use it - I figure its worth a try, or what do you think?

 

You will probably need a stiff brandy after this one "hey"?

 

Thanks for any help.

 

[Johan Bornman]

Ai' date=' ai, I stopped off at the workshop last night to see for myself whats going on.

 

Snip snip snip snip

 

I just read the bit about ammonia, phoned and asked the mechanic if he knew about it, he said "No" but he will try it if I can get him some and tell him what strength to use (must he dilute it ir not).

 

To be honest he didnt sound very hopefull.

 

So, please Mr Bornman (or anybody else) where do I get this stuff, it dosnt sound like you just go to the local supermarket for it, and how do we use it - I figure its worth a try, or what do you think?

 

You will probably need a stiff brandy after this one "hey"?

 

Thanks for any help.

 

[/quote']

 

You are wasting your time with the ammonia, read my explanation above here. The area of attack is simply too small.

 

However, I have no doubt that you want to give it a shot. Buy it from Pick and Pay. It is marketed as Scrubb's Cloudy Ammonia and available in the detergent section on the bottom shelf by the funny drain cleaners and stuff.

 

Easter is upon you. Bite the bullet and drill. If the cover holes are too large, put a washer in. I can't see the job, but I am sure you can do it for far, far less than R8 000. If you can access the screws without dismantling the engine, it is a DIY job. Apply patience, logic and precision instead of ammonia, W80 Q20 and magic potions

 

 

[widget]

"Oh Okay", thanks, it seems quite east to obtain then.

 

........I am gonna give it a go, so I will drop it off later with them, personally I dont think its going to work either, but I feel its worth a try anyway.

 

If not, tomorrow I guess I will have to give them the go-ahead to drill.

 

Johan, its definately not a DIY job for me, believe me, I have no clue about this sort of thing and my tool box consists of a hammer and a bent screwdriver I used last to stir some paint.!!

 

I am going to ask about the washers though, sounds logical.

  

[gummibear]

Thanks Mr JB

You explained this all so well.

My veiw is if you try it yourself with a few buddies and get it right you save a lot of money.If you screw it up it wont cost more than the original engineering cost.so take a shot at it.

[widget]

Well Linex, just called to say the engineering company had finished and they would collect the motor and put it all back together - should be ready tomorrow afternoon.

 

The engineering portion was R2700.00 which included the removal of the corroded grub screws and the fitting of 8 x helicoils.

 

I thought it was pretty fair what do you think Johan.?

 

..............and by the way, whats a Helicoil.? - I understand its a type of thread?

 

They said they would let me know on the cover issue later if they can re-use it.

 

So it looks promising for the weekend.! 

 

.............and Yah, the ammonia did zip, except give the mechanic an itchy nose I hear.!

 

 

[Guest Big H]

Widget, a Helicoil is a "spring" that they theread into the enlarged hole giving it a new "thread". The coils of the "spring" gives it a new "thread".

 

http://www.uni-coil.com/products/COIL_new.jpg

 

 

 

Big H2008-03-18 08:26:23