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Mercarb Carburetors

W

Wotan

Contributing Member
Hello there,
on my `76 850Mercury is one of the Carburettors, the bottom one, heavily worn.
Somebody used aggressive tools to clean the low idle/choke system.
I have tried to order a replacement, a 2nd hand one in good condition, which carried the ID code 6071 A11
Permanent problems with the shipping there.
Now I found a new one! Here on MarineEngine.com.. Here the ID code is 6071 A4 The outside dimensions and connections appear identical, so A4 to A11 is all about jets?
Anyhow, it appears MarineEngine.com as well as Boats.net do not ship outside the US.
Does anybody here have an idea how to order spare parts in the US for Europe?:confused:
Some years ago it was plain easy...
Maybe someone has a suitable carb sitting in the corner? Could we make a deal?

All the best,
Stefan
 
The one I had ordered was from eBay actually, but it was just the seller lazy probably with the shipment.
Ed, one in this list is actually fitting.. -by view! It is called here `WM 5-3´ for 85HP. Another was called `A11´, and the one that failed to send.. also for 85Hp was an `A4´
By looks they are all identical.
Can someone enlighten me on this matter? Are they the same just carry different assigned codes?
 
I believe you need to use the WM-XX number that designates the venturi size you can allways install the proper jets and nozzles. What is the WM numbers?
 
I have not yet found any stamped in number on the carb unfortunately.
The carbs that were offered to me were called A4 and A11
The one in your proposed add is now called A33... and they propose it for an 80Hp. Mine is a 85Hp 4cyl
The WMXX value I have no idea of how to find out. It is confusing
 
The parts diagrams shows A 4 11 27 33 42 58 the WM number is usually on the upper edge of the mounting flange on the carb I showed you second to last pic.
 
From what I am seeing the WM-5 is on the 80hp models what is the serial number of your motor? there may be a slight difference in the venturi size that is the narrowest part of the carb throat where the nozzle sticks up.
 
Hi kim,
My serial number is 9124312
The carb in your link of eBay was mentioned to be for an 80Hp, and it is a WM 12.
It is a pity that these details do not appear in any repair manual. I have found on eBay another WM 5-3, exactly the one mounted and scratched and I ordered it. So at least I have 2 identical ones.
It would be great, since obviously some people were playing around with the motor already, to find out which carburettors are supposed to be mounted, -for next christmas...
 
That is the carb I was looking at, -and they won´t ship outside the US..
I have not checked the jet sizes yet! I will do.
I will make sure that both carbs are equipped identical, and then it is time for trying out!
Yes, the motor was made in Belgium
 
Wow, thank you very much!
As it happens I just closed on a bottom WM5.
This set of carbs you mentioned are WM3. I stick now first of all with my WM5ers, but would the venturi size be different at those?
 
I cannot say if the venturies are the same my guess would be yes. There was a touch of insanity in the mercury engineering department they did alot of small changes even within the same year that is why you use the serial number when looking up parts.
 
I believe that I am on a good path if the top and bottom carbs are identical.
Once I have the motor running, -even at idle.. and the timing right.., I can go for a testdrive and see performance.
This motor was supposed to be an XS850, but I doubt that it still has that performance after some mechanics tried their luck and spare parts are rare.
I see what I can get out of the motor, and will probably try from there a small tuning.
 
Oh yes, I have the Clymer´s, which helps at the rough and tough bits, but leaves you alone when it comes to details and specifications
 
The top and bottom carbs are identical except where the throttle linkage is connected. That's why they have a different model number on the same engine. (Remove the throttle connection and they are identical.) Venturi wise, they come in two sizes: the 'normal' one, and the one made for the 50 hp triples (to derate them). It's obvious which is which if you have them side by side.

From the dozen or so that I have, the basis bodies are all interchangeable--just screw in the correct air and fuel jets (which is a breeze on these used friendly carbs). Two bolts--easily accessible from the front--attach them, and you can change the float needle without removing the float! How nice. My only caution with these is that they are extremely dirt sensitive, so you need a first class, 10 micron filter right before the carb(s).

Jeff

PS: I use three of them on my heavily modified triple.
 
Lightly surface the mounting flanges on the carbs on a glass table with 220 grit paper just pull the carb in one direction only until it all shines the same. Do not over tighten them down just pull them in slow and even to nice and snug. Make sure both carbs open up exactly the same time and then follow the instruction for adjusting the throttle pickup from the spark advance lever then check Max timing advance is correct.
 
Thank you fastjeff!
That gives me some confidence about the right carbs.
I am going to change the needles as well, but I noticed that they are easily flooding, on the lightest pressure on the bulb. Is that a weakness of the carbs, or indeed the needles?
Dirt sensitive with these simple 2 large jets? I thought they would be rather rough going..
I have fitted an extra filter and water separator anyhow
 
Thank you Kim,
With all your good advise I am now confident to get the job done! .. if then finally the new carb arrives!
On the scratched one actually the tiny pressed-in brass jets have disappeared! I have no idea how they managed that...
The one just in front of the venturi for the idle system, and the one at the flange to the powerhead, delivering pressure to the choke.
I do not know what effects these have, but I blame them for not achieving idle
 
You can buy new jets on this site. Ditto and a new needle (but not the seat--they are fixed).

Lower the float level a 1/16 inch at a time until she stops flooding. I clamp my carbs in a vise and pressure them up from my test tank--much easier that way!

Jeff
 
Hooray, I received today my 2nd hand WM 5-3 lower carburettor!
Now comes the enlightenment.. also here is a tiny brass jet missing, like in the one I want to replace!
It is about the tiny hole on the inside just level with the plastic venturi. On the top carb there is a tiny brass jet pressed in, here it is not.

Is it probably a general thing with the lower carbs?
 
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