Balancing Carbs on a 91 Merc 200

[floater88]

I'm trying to balance the three dual carbs on my 1991 Merc 200 hp. The Carbtune manual says to remove the plugs on the intake side of the carbs and hook it up there. On my motor there looks too be three tiny hoses attached to these ports I could use. Two are on the port side and one on the starboard side. Does anyone know what these tiny hoses lead too? I can't find where they terminate. Would these ports also be the ones I could use to balance the carbs? Thanks

[25two.stroke]

No need to. Take the airbox off. Look down the bores and see if any plates are open with the throttle all the way back at dead idle. If one or more is then do the following:
Make sure the roller turns freely on the throttle cam (no pressure on the bottom carb throttle shaft).
Loosen the screws on the top and middle carbs and let the throttle plates close to match the bottom one.
Tighten the screws to secure all 3 carbs in sync.
Re-check to make sure you didn't pull any throttle plates open when you tightened the screws.

Done. Its not a 4stroke with butterflies that independently adjust per cylinder to balance vacuum. If you have uneven vacuum between the cylinders with all the throttle plates shut then you have a problem. Either bad reeds or bad rings. Moreover; some of those intake manifolds are cross-drilled so behind the throttle plate different cylinders can share air+fuel. Each butterfly is not sealed directly to a cylinder like a 4stroke. So you never get a true vacuum reading.

Correct me if I am mistaken, but this is how I understand it and how I balance 2strokes daily. Maybe Chris Carson has an opinion on this?

[floater88]

Ok great info thanks. I will give this a look later today thanks

[pcrussell50]

Ok great info thanks. I will give this a look later today thanks

In the manual of your Carbtune Pro it also says that while it can be used to balance carbs on two-strokes, that usually isn’t done by using manometer devices. It’s usually done on two-strokes the way “25” said… by visually adjusting butterflies.

I have a 1990 V6 200 myself, btw. Mine is the last of the 2.4 series. Yours is probably a 2.5.

I have a Carbtune Pro that I use to tune my carbureted four stroke DOHC four cylinder Mercaha 90. It’s amazing for that. Way better for that 1700cc motor than the liquid manometer Motion Pro Sync Pro. I should say that the Motion Pro is a quality product and the owners are good with product support. The main problem is it was designed for DOHC-4 motorcycles with 500-750cc. With the big vacuum pulled by 1700cc it would suck the fluid out or suck hard enough to create bubbles. With the Carbtune these are non-issues. Love it. 25, if you don’t have a vacuum mate, you should consider a Carbtune Pro.

-Peter

[floater88]

Thanks Pc. I read your other posts on Continous and that is why I figured I should check too see if my Merc needed it as well. I runs great when it's running but it's sneezing when you try and start it now and I sometimes stall out at low idle coming in to dock. I've never rebuilt the carbs but do use the Seafoam in every tank fill up. Thanks

[pcrussell50]

Thanks Pc. I read your other posts on Continous and that is why I figured I should check too see if my Merc needed it as well. I runs great when it's running but it's sneezing when you try and start it now and I sometimes stall out at low idle coming in to dock. I've never rebuilt the carbs but do use the Seafoam in every tank fill up. Thanks

Sneezing is usually a result of leanness. You want to make sure your fuel lines from your tank through your motor are not leaking/sucking in air. A quick and dirty test here is to take the covers off the engine and pump the primer bulb firm and look all around the carburetors and the fitting where fuel plugs into the engine for drips or bubbles or hissing. You want your fuel lines both outside the motor and under the covers, nice and tight and leak-free. I'd start with that.

-Peter

[floater88]

Thanks Peter