How to tune dual carb setup

[DSMBoater]

Hey guys I have a question about my '74 merc 650 3 cylinder that has the dual carb setup. I have read the service manual that explains how to tune the idle mixture screw on the carbs- but one important piece of information is left out. Do I have to use 2 screwdrives and simultaneously turn both screws to tune them at the same time? Or do I just do top carb first then bottom? Thanks!

 

[Chris1956]

Re: How to tune dual carb setup

I would recommend you tune them alternatively for best idle speed and smoothness. Now they may be a bit too lean to accelerate. If so, open top carb 1/8 turn and test acceleration. If not satisfactory, open bottom carn 1/8 turn and retest. Repeat sequence, testing after each adjustment.
Be thankful you have only two carbs. My V6 has 6 adjustments.

 

[Faztbullet]

Re: How to tune dual carb setup

First it has to be in a barrel or backed into lake due to back pressure, and you adjust bottom carb first then top. Let engine stabilize for a minute or two after adjustments and on final adjustment open idle screws a 1/8 turn.

 

[jimmbo]

Re: How to tune dual carb setup

One minor detail has been forgotten. The adjustments require the engine to be in forward

 

[JB]

Re: How to tune dual carb setup

What Manual are you using?

 

[DSMBoater]

Re: How to tune dual carb setup

Im using the Seloc manual, not really in-depth. I will probablly give this another try on the 4th this week... Unless the wife gets pissy and we just fish instead lol..

 

[JB]

Re: How to tune dual carb setup

We recommend the factory Service Manuals, DSM. Aftermarket manuals are okay for the simple stuff, but often just don't get the details of complicated procedures.