Carb tune question

[phebus1]

When tuning my carbs, I have always adjusted to the best idle under load, and then opened them up another 1/8-1/4 turn.

Question is, how do you know that you aren't a little too rich? I know the symptoms of a little lean with a stumble on acceleration, but short of fouling plugs, how would one know that they weren't a little rich? I know rich is better then lean, but I am a consummate tinkerer and would like to get them right on.

Thanks

 

[79Merc80]

Re: Carb tune question

What engine are you talking about??

 

[Silvertip]

Re: Carb tune question

1/8 open from best loaded idle will not foul plugs. 1/4 open won't either but might affect the actual idle quality.

 

[ajgraz]

Re: Carb tune question

1/4 turn past best idle in Winter, 1/8 turn in Summer. Carbed OB ain't gettin' any more spot on than that.

 

[CharlieB]

Re: Carb tune question

Idle mixture only needs just enough additional fuel for crisp acceleration, any more than that is actually just a waste of fuel.

Start witih 1/8 more than best idle under load, if accelerations is crisp you can lean each just the bladewidth of the screwdriver blade slot, repeat acceleration test until you get just the 'slightest' hesitation then reopen to the last setting.

NOTE: Additional load WILL require MORE fuel. Another passenger, loaded ice chest, pulling a tube or skier, any increase in load will create the demand for slightly more idle mixture for crisp acceleration.

So readjusting for ideal mixture is a catch-22 situation, only good IF the boat is always loaded the same. So leaving the idle mix at a blade width MORE than idle may be a better idea.