where to connect vaccum gauge?

[Happygolucky]

From what I’ve seen, the best way to adjust the Idle mixture is to hook up a vacuum gauge and find the highest stable reading - looks easy enough .. only .. where do I connect the gauge on my 5.7l Mercarb engine????
TiA

 

[Scott Danforth]

there may be a 3/8" NPT port in the manifold, however generally, Marine engines do not have a vacuum source as it is not needed.

the easiest way to set RPM is with an unlit propane torch and a tachometer.

wave the unlit torch over the carb opening. if the RPM's increase, you are running a bit lean. if the RPMs drop, you are running a bit rich. if they dont move at all, you are just right.

 

[Happygolucky]

Thanks Scott! So I just remove the flame arrester and wave the unlit ! gas torch above the carb !?

 

[Scott Danforth]

Yep,

Been adjusting carbs that way for almost 5 decades

 

[flashback]

It works well but just don't get too enthusiastic with it, propane will collect in the bilge if you over do it..

 

[Happygolucky]

It works well but just don't get too enthusiastic with it, propane will collect in the bilge if you over do it..

sounds like a good idea to have the blower running then

 

[Happygolucky]

Yep,

Been adjusting carbs that way for almost 5 decades

and I’m only starting..!

 

[flashback]

Just don't set the torch aside with the valve open when you fiddle with the mix..

 

[Happygolucky]

would this be a possible bolt to remove and put the gauge into ?

 

[Scott Danforth]

You can remove that and buy a fitting

 

[airshot]

That carb looks pretty crud covered, think I would clean that up if it were mine

 

[nola mike]

Yep,

Been adjusting carbs that way for almost 5 decades

huh. never heard that one.

 

[Happygolucky]

That carb looks pretty crud covered, think I would clean that up if it were mine

It has crossed my mind.. once the season’s over

 

[Happygolucky]

You can remove that and buy a fitting

Ah perfekt, think I’ll go down that route then.. as I don’t have a propane torch anyway

 

[chs marine service]

Ah perfekt, think I’ll go down that route then.. as I don’t have a propane torch anyway

im sure you dont have a fitting either. the torch will probably cost as much as the brass fitting.