Lumpy idle after carb rebuild | Holley 2300 | Volvo Penta 3.0 GS

[baker556]

There may be a vacuum fitting plugged on manifold

There is vacuum supplied through a small tube for the choke pull off

Prob can put your gauge on there and just force the choke open

Can also just tune it by ear or rpm when you go way lean and way rich it will stumble In Between these two extremes is best idle usually

Is it possible to use the line that goes from the carb to the top of the rocker, bit like a PCV?

I don't think there is anything from the choke.

There is this line, I could TEE into?


Is that a fuel or vacuum line?

 

[Lou C]

The vacuum line if using to set idle mixture has to be manifold vacuum that is below the level of the throttle plate. If there’s no such fitting in yours just use a good digital tachometer; that’s the other acceptable way to do this

 

[Scott Danforth]

How do others test this then? There is various youtubes showing this on other holley marine carbs?
Could I tap into any vacuum hose?

You take an unlit propane torch.

If you wave it over the carb throat and the RPm increases, you are a bit lean

If you wave it over the carb throat and the RPM drops, you are rich

Marine carbs do not have vacuum ports

 

[baker556]

Wanted to come back to this for anyone in the future having similar issues.

Everything is now working, although there is probably some fine tuning required.

As advised, I used a compressor to blow out all passages in the carb, put this back together with a new kit - the new kit had different numbers on the needle assembly would this do anything different? 110 old to 101 new.

Thanks for everyone's help.