Idle orifice question.

[steviecops]

I have just stripped down the carbs on my 1980 Johnson 55 to clean and rebuild.<br /><br />In my manual, it says the pre 1980 engines were fitted with 0.045 idle orifice jets, but that these engines had a bad idle. So, the 1980 on engines were fitted with a 0.046 jet, which improved the idle. Carbs with these bigger jets had a letter E stamped after the number on the carb.<br /><br />My carbs don't have a letter E stamped on them, and when I took the idle orifice jets out to clean them, I noticed that they had the number 48 stamped on them. Does this mean that the size of the jet is 0.048? If so, should I leave them in, or replace them with 0.046 jets?<br /><br />Thanks in advance.<br /><br />Steve

 

[R.Johnson]

Re: Idle orifice question.

You have it right! a jet stamped #48 is .048 As long as you are cleaning the carbs, I would stay with the #48's to start. here is another problem that sometimes shows up, you can come across a jet where someone has opened up the orifice, so you might want to check yours. I say this because you have found someone has changed these jets before. One way to check the size is to use 2 drills as a go- no-go guage. The drills you would need are a #56=.0465, or 1.18mm, then a #55=.052 or 1.32mm. I don't want to muddy the waters here, but this will show what you have, and where your at. On a sound engine, I would not expect much difference between a #46, or #48 jet.

 

[steviecops]

Re: Idle orifice question.

Thank you for the advice.<br /><br />I'm happy to leave the .048's in there as the engine was fine last time it ran. Just a slightly rough idle. I'm rebuilding the carbs after tracing a non start problem with the help of the good people on this message board.<br /><br />Thanks<br />Steve

 

[WillyBWright]

Re: Idle orifice question.

What kinds of outboards are prevalent in England?

 

[steviecops]

Re: Idle orifice question.

Hi Willy<br /><br />The OMC engines have always been popular over here, as have the Mariner/Mercury engines.<br /><br />Our Coastguard, (R.N.L.I), use Mariners.<br /><br />The Suzuki/Honda 4 strokes are becoming very popular now though.