Replacing stock reeds with Boyesens. Need to replace/resize jets. HELP!

[jaykibo]

I recently installed model B144 Boyesen Reeds in my Evinrude 115hp V4 1978 model (model number 115893c. I believe this is a Crossflow type).
I had read in several places that a replacement jets (or resizing jets) may be needed. I also found a few places that said it didn't matter.

I'm certain some engines it doesnt matter but for my carby engine im sure it does. Indeed, after the installation I switched the engine one and it was popping/backfiring at idle so I immediately switched it off.

The instructions for the reed installation says:
IMPORTANT-CARBURETED ENGINES ONLY: STEP 10 MUST BE FOLLOWED OR THE WARRANTY IS VOIDED. USE THE PROCEDURE SPECIFIED FOR YOUR TYPE OF ENGINE. 10. BACKFIRING (a lean condition in the idle circuit, sometimes described as a lean pop, coughing, or sneezing), will cause REED DAMAGE. This MUST be prevented by one of the following methods: A. Carburetors with IDLE AIR JETS controlling idle: EVINRUDE and JOHNSON engines - downsize idle air jets 5 sizes {5 thousandths of an inch}. MERCURY and MARINER engines - downsize idle air jets 2 sizes (4 thousandths of an inch). B. Carburetors with LOW-SPEED FUEL JETS controlling idle: Increase 2 sizes {2 thousandths of an inch}. C. Carburetors with IDLE MIXTURE SCREWS: Richen by turning counterclockwise 112 to 1 turn out more than stock setting. D. On some worn or modified engines, no adjustment will be necessary.

Problem is, I dont know what sort of carburetor my engine has. Can anyone help me out here? I believe the jets are fuel jets so I can simply drill out the jet to get it to the right spec, but again, im not sure about this. I would much prefer to drill out the jets as I have spare ones from a different set of carbys I have lying around.
Also, does anyone know which jet will need to be resized? I dont know what is looks like if someone could please point it out to me in the pic below that would be greatly appreciated.

EDIT:
I have successfully installed the jets now. For those of you who are reading this thread to find out what you need to do, I have summarised the main points below.

- Below information is for a 1978 Evinrude 115hp V4 (Crossflow) Model: 115893C or 115893
- Below information is for installing Boyesen aftermarket reed valves (model B144)
- There are 2 idle jets per carburetor (4 orifices/jets in total)
- They are FUEL orifices, so when installed Boyesen Reeds you need to go UP 2 sizes
- Stock PORT orifices are #28. Stock S/board orifices are #27.
- Replace the PORT orifices with #30. Replace the s/board orifices with #29
- Port orifices are the ones on the left when looking at the bow

Hope the above helps!

 

[Daviet]

Re: Replacing stock reeds with Boyesens. Need to replace/resize jets. HELP!

Well, the way I am reading it is that you are working with the idle AIR jets, #6 below. The other jet is a fuel jet, #10 below.
I would think #6 is the one you need to work with. I am sure others will chime in and help out.
:: iShopMarine.com ::

 

[jaykibo]

Re: Replacing stock reeds with Boyesens. Need to replace/resize jets. HELP!

Thanks Daviet.
Do you know if I need to change/modify both jets? Or just the idle?
I suppose if its just the idle jet (and it is indeed an air jet) then I would need to replace as I cant drill it to a larger size.

 

[Daviet]

Re: Replacing stock reeds with Boyesens. Need to replace/resize jets. HELP!

Well, I guess since the instructions state "idle air jets", I would think you modify the air jets.
The other orifice is the high speed jet and passes fuel, not air.
I will say that I have never done the above procedure and am only going by what I have read in your post.

 

[jaykibo]

Re: Replacing stock reeds with Boyesens. Need to replace/resize jets. HELP!

Well, I guess since the instructions state "idle air jets", I would think you modify the air jets.
The other orifice is the high speed jet and passes fuel, not air.
I will say that I have never done the above procedure and am only going by what I have read in your post.

Thanks Daviet. I agree.
Poring through the Boyesen instructions with a fine tooth comb I read it this way:

This MUST be prevented by one of the following methods:
A. Carburetors with IDLE AIR JETS controlling idle: EVINRUDE and JOHNSON engines - downsize idle air jets 5 sizes (5 thousandths of an inch). MERCURY and MARINER engines - downsize idle air jets 2 sizes (4 thousandths of an inch).
[OR]
B. Carburetors with LOW-SPEED FUEL JETS controlling idle: Increase 2 sizes (2 thousandths of an inch).
[OR]
C. Carburetors with IDLE MIXTURE SCREWS: Richen by turning counterclockwise 112 to 1 turn out more than stock setting.
[OR]
D. On some worn or modified engines, no adjustment will be necessary.

To me, it looks like I need to execute A, B, C or D. In this instance, I believe it's only A I can execute. So I will need to reduce the air jets down by 5 sizes on my Evinrude, leaving the other main jet alone.

Looking at the parts diagram (above) I see that #6 has part numbers 322936 and 317474 for the 115HP variety.

The 'Orifice Idle' 322936 port part is a .028 diameter orifice. 317474 is the s/board part and is .027 diameter.

So if I were to go down 5 sizes (5 thousandths of an inch) then I would need 0.23 diameter for port and 0.22 for s/board orifices.

Can someone sanity check my logic above please?
Many thanks!

 

[clanton]

Re: Replacing stock reeds with Boyesens. Need to replace/resize jets. HELP!

The jet size may not be in thousandths. Some jets are marked for the amount of fuel flow thru the jet.
You should be able to look at the carb, and location of jet to tell if air or fuel jet. The main jet is a fuel flow jet. Some folks stick a tooth pick in the air jet to make it richer for a test.

 

[jaykibo]

Re: Replacing stock reeds with Boyesens. Need to replace/resize jets. HELP!

The jet size may not be in thousandths. Some jets are marked for the amount of fuel flow thru the jet.
You should be able to look at the carb, and location of jet to tell if air or fuel jet. The main jet is a fuel flow jet. Some folks stick a tooth pick in the air jet to make it richer for a test.

Thanks Clanton.
It is an air jet. I will need to make it smaller. I searched the net for a part number for a smaller size but couldnt find it for the life of me! I rang around my local marine dealerships for Evinrude parts and the best I could find was a #23 (0.023 diameter), I need #22 and #23. Plus, this part is not in the country and will need to be special ordered to Australia.

So I am thinking of actually putting a drop of solder in the jet and re-drilling it. I've read on the net that some people do this and works fine for them. Im hoping this would be a temporary option until I can source #22 and #23 air jets, but it may need to be permanent

 

[jaykibo]

Re: Replacing stock reeds with Boyesens. Need to replace/resize jets. HELP!

Hi everyone.
I took the jets out of the carburetors today.
Looks like both port and s/board carbys are #27 (0.027 thousandths of an inch, diameter). This would mean IF they are air jets then I would need to replace them with #22 (0.022) jets. But I still dont know definitively if they are air or fuel jets as someone from another forum pointed out. They do have a plug screw which closes off the hole, but that doesnt mean it is just an access hole and the air could be coming from elsewhere.... I just dont know anymore! Can someone please help me out?
The carby part number stamped on the side reads: 888862-D

The picture of the carby and jets are here: Photo Album - Imgur

 

[jaykibo]

Re: Replacing stock reeds with Boyesens. Need to replace/resize jets. HELP!

accidental post

 

[jaykibo]

Re: Replacing stock reeds with Boyesens. Need to replace/resize jets. HELP!

 

[Daviet]

Re: Replacing stock reeds with Boyesens. Need to replace/resize jets. HELP!

Those are the idle air jets in post #8.
If you can't find the ones Boyesen recommends, I would call them and ask them the proper procedure for getting the correct jets.

 

[Tim Frank]

Re: Replacing stock reeds with Boyesens. Need to replace/resize jets. HELP!

Those are the idle air jets in post #8.
If you can't find the ones Boyesen recommends, I would call them and ask them the proper procedure for getting the correct jets.

^^^^^ +1 .... call them.

I have a chart that gives part numbers of these jets based on size.
If you find that they are fuel jets, I'd still get new jets unless you have access to at least a lathe.
The external thread is 8-32 so you could make a small fixture to chuck the jet.
Not easy sizes to drill however.

Part numbers per my chart :
IF they are air jets....Port number is a #23 orifice....OMC part # 326188 Stbd is a #22 .... OMC part # 331934
IF they are fuel jets....Port number is a #30 orifice....OMC part # 317473 Stbd is a #29 .... OMC part # 322776

 

[iwombat]

Re: Replacing stock reeds with Boyesens. Need to replace/resize jets. HELP!

Guys, if I'm not mistaken those model carbs are fuel jets, not air jets. The models with the air jets have them in the throat, not on the side.

 

[iwombat]

Re: Replacing stock reeds with Boyesens. Need to replace/resize jets. HELP!

Air jet type carbs. See #7 - the air jet

 

[Tim Frank]

Re: Replacing stock reeds with Boyesens. Need to replace/resize jets. HELP!

Guys, if I'm not mistaken those model carbs are fuel jets, not air jets. The models with the air jets have them in the throat, not on the side.

That's what I thought, too, but I'm not 100% certain;that's why I think calling Boyesen is the right answer.

 

[iwombat]

Re: Replacing stock reeds with Boyesens. Need to replace/resize jets. HELP!

Calling the manufacturer is never the wrong answer.

 

[phillnjack2]

Re: Replacing stock reeds with Boyesens. Need to replace/resize jets. HELP!

to mean fuel spitting back is a case of reeds not shutting correctly.
ive known loads of bikers change the reeds especially moto cross and never changed the jets just because of changing reeds.
the reeds don't change the fuel ratio of air mix, they are just supposed to give a better intake and a better seal.

phone them and ask why they have to be changed, arethey telling you that youl have less performance by having less air = less fuel = less power ?


phill

 

[iwombat]

Re: Replacing stock reeds with Boyesens. Need to replace/resize jets. HELP!

With the boyesons, if you get popping out the carb you can ruin your brand new reeds. They usually need a little more fuel at low speeds.

 

[Tim Frank]

Re: Replacing stock reeds with Boyesens. Need to replace/resize jets. HELP!

Right. They are just trying to enrich the idle mixture a bit.

 

[phillnjack2]

Re: Replacing stock reeds with Boyesens. Need to replace/resize jets. HELP!

a touch richer maybe , but no way to change the jets down by so much.
give them a phone call.