TOPIC: 1884 115 Carb questions

I have just pulled the carbs on my '84 115 (s/no 6480055) & have a couple of questions.

1) There are 3 different numbers on all three carbs WMK41 1A (the 1A seems to be stamped over 3A - top carb), WMK29-3 (middle carb) & WMK41 3A (btm carb). All appear, as far as I can tell, to have 074 main jets in them. As can be imagined they have been a bit 'got at' by knuckle draggers from the bugger-up team over the years. Question is are these OK to use or should I try to get all the same?

2) They have the "back drag" (to quote the Merc manual) system on them & I have seen posts on this site to remove the system I believe as it can cause problems. If I am correct in this do I just take the bleed hose off & seal both ends (or block the tube I suppose)?

The motor suffered from a terrible flat spot after idling last season I so I am going through the whole fuel system from the tank (28 US gallon coffin) up through the water separating filter (new quicksilver one), fuel pump ('oval' type - overhauled) & now carbs. To date I have not really found anything significantly amis.

Edit:

Just checking the beast over & I have spotted this split pipe (see picture). I think it must be an oil transfer pipe lifting oil to the top bearing as it runs right to the bottom of the block? Other than possibly leaking oil what effect would this have on the running of the thing? I would think cyls 1 & 6 would run weak?

One thing I have spotted is that it must have had a new stator shortly before I bought the rig last year as the stator wiring, as can be seen here, is like new, unlike the rest of the motor which has been sprayed with something like WD40 that has sat on the wiring & made is swell a bit & go soft.

Any help gratefully received

Geoff UK

Geoff,
The carburetors should all have the same WMK number followed by a 1, 2, & 3 regarding their placement on the beast.
1 being the top carb.
I would have to research to identify which specific set of WMK carbs were original on the '84 115.
.074 mains 'sounds' correct.
To disable the 'back-drag' system you can simply remove the jet from the float cover or remove the hose from the float cover.
Can plug if you want I guess, but not required.
The flat spot could be one of two things usually.
Either too lean settings on the idle jets or improper sync between the primary pick-up and ignition timing. Try opening (counter-clockwise) all three of the idle jets 1/8th turn and try to accelerate. open them all the same again if this doesn't eliminate the flat spot. If you get to where you have opened all three idle jets about 3/4 turns total and still have the flat spot you probably will find the problem in the synconization of timing to carburetors at the off idle area.
The broken tubing needs to be replaced and is critical to the survival of the top main bearing. With it cracked, etc the fuel mix also leaks out and gets on the wiring consequently swelling the insulation and ruining the rubber cowling mounts.
Thom

Thanks Thom, I don't what, if anything, I can do about the carbs, they are not common over here 2nd hand.

Re. the back drag & excuse me for being thick here, but if you just disconnect the pipe then surely the carb is always sucking air (I know that is what it does anyway but I thought this was the cause of the problems) hence my idea of blocking the pipe, so in effect it is as if the pipe union had never been drilled into the carb body - or am I totally wrong here??

I understand your logic, but I have been told to simply remove the ability of the jet to meter the flow.
The problem with the jet and hose are that when activated it causes a lean condition at mid-range throttle. It was a fuel consumption economy attempt that left mid-range too lean. Mid-range is after the timing has fully advanced and the carburetors are still closed or barely open. A very hot and lean situation to begin with. Then with the mid-range (back drag) disabled it becomes even leaner and leaner leads to melted pistons, etc.
I was told to do it this way by several much wiser than I and I run my Stacks real hard with the mid-range jet disabled.
Thom

Hey Geoff,

Its probably just as easy to plug that rubber back drag tube, permanently. I used a plastic pellet but a BB would work just fine. I tend to think like you do and leaving big holes where a hose was once connected just doesn't sound like a good thing. To me, it would make a carb run even leaner.

Thom is a master though, and I'm sure his advice is sound as well.

Also, while you're at it take the electronic idle stabilizer off that motor and chuck it in the garbage. Stick to manual timing and mechanical advance.... no need for electrons in that equation.

I had the same motor, could have been its sibling. Great motor for sure.

Get that tubing fixed before you overheat your upper crank bearing.

Good luck.

And,...I forgot to mention: Write direct and I can probably hook you up with a matching set of carbs or whatever you need.
I have about (5) 2 foot x 2 foot x 3 foot bins full of them.
All just dying for an European Vacation.

Thom

Thank you for your replies Gentlemen, Thom I will send you an email.

Can I just remove the electronic idle stabiliser (I am not convinced mine works anyway as I have problems getting it to idle), if so what to I do to compensate for it not being there?

Thom I wish you would change your signature picture - it's just not fair bragging about the beast of yours!!!

Geoff,
Yes - simply remove the Idle Stabilizer. That is all there is to it.
In regards to idle quality - if all the compression readings are relatively even I would suggest going back through the link-n-sync process.
I'm going to try and attach the link-n-sync process for adi fired Stack-6s.
It consists of (5) pictures so there will need to be this e-mail and (2) following to post them all.
Note: the following pictures contain the Primary Pickup Timing numbers for a 140 not a 115 so be sure and follow the 115 numbers found in the last picture in this series.
Thom

Hum-m-m-m? Looks like only one picture posted.

RATS,...Looks like one picture per post so here is #3 of 5.
Thom

#4 of 5

And #5 of 5.
Be sure and follow the specific sequence in the pictures.
Thom

To add more than one pic per post, just edit your message to add another.

Thank you Thom, as ever you are more than generous with your time & information. I do have the correct Mercury (OE) manual for this motor & set up the primary p/u latter part of last season, I will do it again though in case I was being a numpty & got it wrong. I seem to remember it was some way out so I changed the settings (adjusting screws seemed to be in their 'normal' places afterwards) but it didn't make a blind bit of differnce!

The info on setting up the butterfly's is good though - I haven't done that yet.

Geoff

Geoff, you should see some of the pics of Dr. Frankenmerc's (Thoms) shop! Towers everywhere, makes you go into sensory overload. I think he's helped most, if not all of us out at one time or another.

And to be fair, there are several others who are also very knowledgeable and equally generous with their time here, dave bernard, 63g3, just to name a few.

I saw his pictures on the last board - an amazing collection, the guy is a real star!

Poor idle can also be caused by missing " bleed inserts "

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on the motors equipped with them they are usually missing.

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I install 8-32 stainless setscrews with the wee hole drilled in them. They will never fall out again.

Fabulous forum, as usual a wealth of informtion shared. Your advice Thom is always eagerly welcomed along with the other masters of these inlines.

In regards to bleed restrictors, I have the attached info from an old service bulletin. Hopefully it helps.

Thom, I have tried to email you but your 'comcast' address keeps bouncing back, so I have sent it to 'hctc' now as well.

Professor, I will bear that in mind about the restrictors, means taking off all the ign system to get to the transfer ports so I will see how I get on with the carbs & timing first. Thanks for the picture Glastron GT160.

Geoff,
I have now received a couple e-mails from you so hopefully my spam guards are recognizing you as a pal.
One I sent to the 'internet.com' addy kicked to me this morning, but there should be the same e-mail at your desk.
I was unable to locate any WMK 41A carbs in my heaps of carbs. I'll bet ther are 500 carbs in those bins.
I forwarded your need to a couple fellows that also keep a pretty good stash of Mercury Treasures.
I can definitely mail you the needed scavenging system tubing if those guys can't include it - if they have the right carb for you.
I 'doubt' that running the WMK 29 as a middle carb will hurt anything though.
My logic is based on the fact that the 29 came on the '79-'80 adi 140 Stack which basically was marketed as the 115 in '84-'88 and used the .074 mains just like your '84.
Hopefully someone has the correctly stamped carb, but based on the similarity between the '79 140 & the '84 115 and the fact that the beast didn't melt-down with this set up last season I would think it is okay.
Compare the black plastic boost nozzle, the configurations of the brass tubes in the venturi, and configuration of the small holes drilled in the butterfly.
note: the bottom carb may have one larger hole in the butterfly.
That is because so much fuel mix slobber falls down there at an idle and the larger hole tries to send it into the cylinders before it all goes to the scavenger system. (at least that is my conclusion as to why the larger hole is in the butterfly of #3.

When I say 'similar' and 'basically' the same I am referencing the only possible difference between the two engines might be a high dome power port piston in the '79 140 and 'maybe' there is a low dome power port in the '84 115.
Perhaps someone can research that for you.

I agree with the importance that the bleed restrictors all be in place and really like the idea of using 8/32" set screws with a small hole drilled into them as a permanent fix.
There are fellows out there that will tell you that the bleed restrictors are unneccesary for good idle quality.
Perhaps that is true on a freshly rebuilt Stack with excellent labyrinths inside the reed blocks, but in the long run - I replace the missing bleed restrictors every time.
Thom

Geoff;
Just finished searching through 3-400 merc carbs , looking for a WMK 41-2. No luck. The only WMK 41s I have are on a 115 like yours.
Got about anything else you could imagine but not those.
Sorry
Tim

I think I have a set of carbs from a 115hp. Take me a week or so to get at them though as we're packed in preparation for moving. I'll keep an eye on this thread. Please post back if you haven't found what you need.

Thank you all for taking the time to help me, very generous of you.

Geoff UK

this is one of those threads you read carefully and learn allot from. Wow! I love it when the Merc gods speak. If you have no luck today I can also check to see if I have any spare carbs. I have a few of these blocks in various conditions so I will bet I have one also. Let me know if nothing else pans out so I am not wasting the effort provided by someone else.

Jim

Thank you Jim, I think one of Thom's contacts has come up with the goods, I just need to get it across the pond to the old country now!

It never ceases to amaze me how much help is available on these forums, IL6's are not some common over here & people who know about them even less so & you can narrow it down even more if you take out the ones who will only help if you hand them a bunch of 10 pound notes!

I have just inadvertantly buggered up the look of the powerhead. It had been sprayed with some kind of damp start oily muck (I am guessing that's what it was) so I thought now was a good time to clean it up. I loaded up a wash gun with the cleaning fluid we use here to clean out auto tranny valve blocks as it cleans well & dries off quickly. So off I go & hit it with the stuff - get called away to answer the phone & come back to find it has reacted with with the oily muck that was on it &, whilst it has cleaned all the oil off, the surface of the motor has a white film coating it. What a mess! It will come off if you work at it but I think that will have to wait till the powerhead is off one day. Goodness knows what the numpty that coated it used. Still at least it is all dry now!