thinking of rebuilding carbs

[amosh]

im thinking about rebuilding my carbs on a 91 2.5l v200 merc outboard. 3 carb setup. in the shop manual it says that the carbs have id numbers with suffixes 1-3 and that the carbs must be installed from top to bottom 123. but i went out to look and see what i was getting myself into, and the top carb is numbered 2 canter 1 bottom 3. do i change them to 123 when i rebuild them or do i leave them the same as they are, because i think this is how they came from factory. dont believe that they have ever been rebuilt. if i change what would it do to them being sync ed up to eachother?

 

[Chris1956]

Re: thinking of rebuilding carbs

The top carb will have the enrichener on it. The other two don't what are you seeing?

 

[Texasmark]

Re: thinking of rebuilding carbs

My manual for a 90 triple shows different jets used on the three carbs and it lists the carb type, WME for example, then a series number like 50 then a #1 #2 #3 assuming that refers to the position on the engine from the top down. In the high speed jet size column the orifice diameter is specified and in some versions of this engine it matters which is where. In others, all three orifices are the same diameter.

Just looking at one carb for example on a 4 cyl engine with 4 carbs. PN is WME-79 but position numbers and orifice sizes are:

#1 (top cylinder) .048"
#2 .050
#3 .050
#4 .052

My manual, which covers the 3 and 4 cylinder, 3 and 4 carbureted I engines, shows the output of the enrichment valve going to a splitter that supplies all carbs with supplemental fuel for starting. On the V engines I have no idea. One would think that if you are trying to start a fuel starved engine, like trying to start one that has been sitting for a month, you want all the cylinders lighting off so you would want extra fuel to all of them. Makes sense to me.

Mark

 

[Dukedog]

Re: thinking of rebuilding carbs

Put 'em back just tha way they are now. V6 Merc carbs/numbers can be a "mind bogglin'" thing ta say tha least...........

 

[Dave1027]

Re: thinking of rebuilding carbs

Just looking at one carb for example on a 4 cyl engine with 4 carbs. PN is WME-79 but position numbers and orifice sizes are:

#1 (top cylinder) .048"
#2 .050
#3 .050
#4 .052

I have heard of this before. Why would you need different size jets for each carb? My '88 100 hp came with .054 in all 4 carbs. Seems Mercury had problems trying to make this engine work right and began dicking around with the jet sizes.

 

[Chris1956]

Re: thinking of rebuilding carbs

Dave, Gravity makes the bottom cylinders on my IL6 run richer than the top ones. Maybe that is the reason?

 

[Texasmark]

Re: thinking of rebuilding carbs

Guys I don't know but what Chris said makes sense. Other thing is maybe the way the fuel is routed from the carbs to the cylinders. Maybe the casting differences in the center do different things to the fuel flow.

But yes on the tuning of this engine. I will agree that it is a sensitive critter but when she is setup right a singing song bird that loves rpms.

Mark

 

[Dallenx]

Re: thinking of rebuilding carbs

Amosh,
I'd say to think about some stuff first then decide if you want to investigate or swap the carbs.

How was the engine running (idle, acceleration, etc.) before the 'carb issues' that brought you to a rebuild?
How were the plugs...black?....fouled only on a certain cylinder?

These answers and others that you may think of could help you decide to 'just put them back'.....or not.
If it was me, I'd want it back to spec but I'd be concerned with getting it wrong and wrecking the engine by maybe running to lean.
Your call my friend.

Now if you want it put to spec then find the spec.
Example:
A manual for s/n's 0G960500 and above shows this for a 200hp with WMV-18 carbs.
Jet - Idle air vent (.038 Top)
Jet - Idle air vent (.028 Center)
Jet - Idle air vent (.032 Bottom)

JET?main fuel (.080)(200-Top-Stbd/Center-Port)
JET?main fuel (.082)(200-Top-Port)/Center-Stbd)
JET-main fuel (.078)(200-Bottom-Port)
JET-main fuel (.084)(200-Bottom-Stbd)

 

[Dave1027]

Re: thinking of rebuilding carbs

Dave, Gravity makes the bottom cylinders on my IL6 run richer than the top ones. Maybe that is the reason?

Thanks for that idea. Of course it does not really coincide with Mark's jet configuration. His jets get richer for the lower carbs so it's completely opposite.

I'm trying to wrap my head around how this gravity thing would work. Let's say that gravity caused fuel pump pressure to be slightly greater towards the lower carbs. You'd think the carbs floats, needles and seats would negate that difference.

 

[Dallenx]

Re: thinking of rebuilding carbs

Depending on the model the enrichment valve will allow fuel from the upper bowl to get down to the middle and lower carbs, bypassing their floats and needles, which allows the extra fuel to get sucked straight in during a cold start situation.
Mercury says that the middle and lower carb jets are set so they supply less fuel at idle (just enough to keep the cylinder lubricated) and that's why you can use the enrichment valve to get started.
Anyway, this is what I've read. I need to go look at mine to see how it's set up.

 

[oldman570]

Re: thinking of rebuilding carbs

Here is a link to a manual for a 200 Merc motor,
Boatinfo - Mercury Service Manual for 135-150-175-200 hp
If you want to rebuild the carbs, just remove one at a time and rebuild it then move on to the next keeping them separate as to which one goes where on the motor top to bottom. This way you will have everything back where they should be. JMO
Oldman570

 

[Dallenx]

Re: thinking of rebuilding carbs

I'm rebuilding my carbs while I wait for other parts so I took a look at the enrichment system.
Mine goes straight from the enrichment valve to the input of cyl #1 (after the carb and before the reed valve intake).
No other part of the enrichment goes to cyl #2 or #3.
The regular post fuel pump line is shared (pressurized equally) between #1, #2 and #3.
Weird....go figure that things are different from one model to the next and from one manual to the next.

 

[Dave1027]

Re: thinking of rebuilding carbs

I'm rebuilding my carbs while I wait for other parts so I took a look at the enrichment system.
Mine goes straight from the enrichment valve to the input of cyl #1 (after the carb and before the reed valve intake).
No other part of the enrichment goes to cyl #2 or #3.
The regular post fuel pump line is shared (pressurized equally) between #1, #2 and #3.
Weird....go figure that things are different from one model to the next and from one manual to the next.

Could it be some previous owner disconnected 2/3 of it? Do the 2 and 3 intakes have ports like number 1? What year/model motor do you have?