Mismatched Jets?? 40hp Johnson 1991

[CalicoKid]

I've got my carbs apart for cleaning/rebuilding due to a flooding problem I had. I believe a misadjusted float was the culprit. However I found another interesting issue:

The high speed and intermediate speed orifices are not the same on both carbs.
The upper carb is jetted 47D high and 33 intermediate; The lower carb is jetted 50D high and 35 intermediate.

The carbs show signs of having been disassambled in the past by screw heads being nicked etc. and are very clean.

Motor is a 1991"EN" 40hp Johnson twin;
Carbs are 432439
I am at elevation 800-900 ft.

Do I have the right orificies? Shouldn't they be the same?

Also, my shop manual states that I should discard the screws attaching the air silencer box to the carbs and replace with new. What is the reason for this? The only thing I can think of is because of the threadlock compound on the screws. Can I clean them and reapply threadlock or is there another reason for new screws?

 

[WillyBWright]

Re: Mismatched Jets?? 40hp Johnson 1991

Use loctite on the screws and you'll be fine. I suspect that somebody put a 50Hp carb on there once upon a time. Who knows, could be a factory screw-up. Look down the throats of the carbs. One may have a smaller venturi opening than the other.

 

[CalicoKid]

Re: Mismatched Jets?? 40hp Johnson 1991

Both carbs are identical. All the casting #s are the same with the exception of the lower having a '1' inside the float chamber and the upper having a '2'.

I figured as much about the screws. Thanks Willy.

 

[ezeke]

Re: Mismatched Jets?? 40hp Johnson 1991

Look at the parts lists; the orifices are supposed to be different.

http://epc.brp.com/default.aspx?brands=ej&lang=E

 

[CalicoKid]

Re: Mismatched Jets?? 40hp Johnson 1991

Thanks for that. It looks like my intermediates are correct then but according to the parts list both carbs should have a 47D high speed... if I'm interpreting it right.

It appears intentional also, someone had scratched the respective jet sizes into the float bowls with an awl or something.

I wonder if there was an OMC service bulletin about this?? Thankyou anyone who can help me! Maybe I'm worried about nothing.

 

[seahorse5]

Re: Mismatched Jets?? 40hp Johnson 1991

:

The high speed and intermediate speed orifices are not the same on both carbs.
The upper carb is jetted 47D high and 33 intermediate; The lower carb is jetted 50D high and 35 intermediate.

Motor is a 1991"EN" 40hp Johnson twin;
Carbs are 432439
I am at elevation 800-900 ft.

Do I have the right orificies? Shouldn't they be the same?

Some models used different jets in the upper and lower carbs.

Your EN outboard is a 1992, not a '91 ! Post the complete model number including the last letter as there are differences in early and late production motors and by model. Then we can look up and see what was original.

 

[CalicoKid]

Re: Mismatched Jets?? 40hp Johnson 1991

You are right it is a '92.. I had a lapse there :lol: Model VJ40TLENJ. Thanks for helping. I have not been able to confirm yet that it should have two different high speed jets.

 

[CalicoKid]

Re: Mismatched Jets?? 40hp Johnson 1991

Anyone else? Is the 50D the proper high speed jet for my lower carb??

 

[boomfunk]

Re: Mismatched Jets?? 40hp Johnson 1991

Bringing up an old thread here, im having issues with finding what rebuild kit i need to use for the same carbs as above .. numbers are -

Carbs are 432439

I cannot find that part# anywhere, what kit will work.. its a 40 jonhson 91

Any help at all would be great appreciated, as so far the boat places out here in Oz havent helped

Im after a rebuild kit