Fixed jet carborator sizes

[Leefy]

Can anyone tell me if going from a size 50 fixed jet to a size 35 fixed jet is making the idle richer or leaner?

 

[dehydrated]

Re: Fixed jet carborator sizes

The bigger number is leaner more air 35 is richer less air

 

[kbait]

Re: Fixed jet carborator sizes

Not an expert, but isn't the fixed jet actually the main(high speed) jet, and that takes over above idle speeds? And the idle circuit has a separate metering needle? I'd think the idle mixture would not change w/main jet size change. And I thought a larger number jet meant more fuel (bigger hole for fuel to flow) and thus 'richer'. But it should only affect above-idle speeds. Again, not an expert. Someone brilliant will chime in.

Good luck!

 

[dehydrated]

Re: Fixed jet carborator sizes

Good point! It would help if we knew what we are working on but by the numbers i figured it was idle jets we were talking about .main jets would be leaner for sure! Maybe we can get more information so we could all be brillant

 

[Leefy]

Re: Fixed jet carborator sizes

Ok, more information. 1985 Evinrude 40 hp model E40TELCO. The idle jets were a size 50. One of my first posts referenced a parts diagram that states it came with 40's in it. A boat mechanic put size 35 idle jets in as he said it wouldn't idle right with the 50's in it. It really really idles bad now with the size 35's in it. I just bought the boat so don't know how it was idling with the 50's but sure know it bad with the 35's. My question again, is the 35's making the mixture richer or leaner than the 50's. It will almost keep running at idle but not all the time. Lots of smoke and lots of jerking. Would assume it is way richer than it was but you know what assume gets you. Going right by an outboard repair tomorrow so thought I would buy different idle jets and try but need to know the results of the different size. I know, I know I could just take it back to the mechanic but it is a 40 mile drive so thought I would try to fix myself first.

 

[archcycle]

Re: Fixed jet carborator sizes

The "fixed jet" you're looking is actually an air bleeder which meters air not fuel, which is why bigger=leaner for that one. The parts diagram says #40 so put #40 in there and see what you get. Making it look like the picture is generally the safest way to go.

 

[archcycle]

Re: Fixed jet carborator sizes

My question again, is the 35's making the mixture richer or leaner than the 50's.

So the 35 is 12.5% richer than the manufacturer recommends and the 50 was 25% leaner than the manufacturer recommends.

 

[Leefy]

Re: Fixed jet carborator sizes

Thank you for the information. I will try and locate #40 jets and see how it works. Maybe even get 45's if they make them. Trial and error. Appreciate the help.

 

[dehydrated]

Re: Fixed jet carborator sizes

Glad you got it all worked out,a little more information always helps

 

[archcycle]

Re: Fixed jet carborator sizes

Thank you for the information. I will try and locate #40 jets and see how it works. Maybe even get 45's if they make them. Trial and error. Appreciate the help.

If I were you I'd completely ignore what that mechanic said and get the 40s unless you put your eyes on a genuine OMC service bulletin that says use something else.

You might stumble onto something good with trial and error, but baseline it at factory settings.

 

[EN2]

Re: Fixed jet carborator sizes

It was several years ago that my dealer rejetted top carb with #37, had #40. It had some minor idleing issues, mainly dieing every so often when trolling. Wouldn't stay running with bottom spark plug lead removed. After the rejet it has been running perfect.