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

[jaykmar]

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

 

[Rocketman14]

#6 on the above diagram is the idle orifice, and item # 10 is the high speed orifice. Orifices can be drilled out using precision drill bits, but I would go one size at a time and try the engine idle performance as I go. In reality, you may be better off taking the engine to a certified boat mechanic for this problem! Altering air fuel ratios on boats is a tricky business!

 

[jaykmar]

Thanks very much for your help gents
I have a set of precision drill bits purchased for exactly this type of job, so I am happy to do it myself. I've rebuild this entire engine from ground up but have always been scared to touch carbys because, well, to me they are too finicky and a little bit of a magic/black box.
However, if I am told which jets need to be drilled out and by how much, I have the tools to get it done!

The jets I have in there at the moment are stock standard. I will be pulling them out to sanity check this.

So the questions I have are:

1) Are the jets air or fuel jets?
I believe this question was answered by rocketman14. If I need to drill them out then they must be fuel jets. Thanks rocketman14!

2) How much do I need to drill out the jets by?
Going by the advice given by Boyesen in the instructions booklet I quoted in my original post. I believe I need to go up in size by 2 thousandths of an inch. Can anyone confirm this?

3) Do I need to do the modifications on both idle and main jets? Or just the idle?
I believe it is just the idle jets. Please confirm.

4) If I were to just throw in the towel and decide to buy the correct jets. Where could I get them from and what sizes?



Thanks again for all your help!

 

[jaykmar]

http://www.seawaymarine.com/
Give these guys a call and see what they recommend, they have the best books for jonnyrudes. They should know the proper jet size depending on the altitude also. Do not run it until you are sure you have the correct jets for sure?

I tried calling them but they were closed. I will try again tomorrow in the early morning. I live in Australia so timing is a little difficult

Also, regarding altitude. I am at about sea level here in Sydney. No altitude issues here.

 

[jaykmar]

I have this question posted up on another forum also and I think between these two thread I have the answer.

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 part is a .028 diameter orifice.
So if I were to go down 5 sizes (5 thousandths of an inch) then I would need 0.23 diameter orifices.

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


P.S. Once I get all this working ill be sure to post up the results, for posterity

 

[jaykmar]

The 'Orifice Idle' 322936 part is a .028 diameter orifice.
So if I were to go down 5 sizes (5 thousandths of an inch) then I would need 0.23 diameter orifices.

Need to replace the above with:

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.

 

[jaykmar]

What I am seeing is the 90 hp has #25 low speed orifices you will want to confirm they are for air bleed or fuel. It looks like they are fuel jets to me because they are covered with a plug. That would make it the B type method according to installers guide for the new reed kit? Seaway is on pacific standard time not sure the time difference for down under. It looks like your 17 hours ahead of us from sydney to seattle 8:00am-5:00pm mon-fri our time = 1:00am - 10:00am tues-sat your time I believe.

Thanks mate. I will try calling them tomorrow morning (my time).

As for the jets. So you think they are fuel and not air?? oh man, now I am TOTALLY confused. I thought they were air. Is there any easy way to tell upon inspection? I am planning on pulling the carbs out tonight and taking pictures. Thanks.

 

[jaykmar]

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 if they are air or fuel jets as kimcrwbr1 pointed out above. 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: http://imgur.com/a/3pBE7

 

[jaykmar]

 

[jaykmar]

kimcrwbr1, I'll have a look in my Seloc manual to see if I can find the chart.
Its almost 1am here. I couldnt sleep so I decided to check the forums... :rolleyes:

 

[jaykmar]

OK, I found the chart in the manual. Its actually a Clymer, not Seloc.

It looks like the jets are getting smaller, so this means its a fuel orifice? That would be GREAT! So that means I would be able to drill out the correct sizes rather than have to buy new jets! woo!
I will just need to increase both jets by 2 thousandths of an inch.
Actually, the port jet in the carby is #27 but the manual says #28, so I may just increase the port jet up to #30.

Pics can be found here: http://imgur.com/a/FUxYT

 

[jaykmar]

Hey guys, sorry for not closing the loop on this thread. There were some other issues I needed to deal before I could look in to this.
Just to fill you in:

- The jets are indeed fuel jets
- I drilled mine out (using my precise drill bit set, putting the orifice in a old drill chuck [which I had removed from the drill] and a drill press)
- The engine is idling pretty well now while on the muffs, I am quite happy. But just to be sure I have ordered the actual size orifices that I need (#29 and #30). I dont want to take it out on the water until I install these).
- I am confident things will run well out on the water once I put in the proper orifices.

Once again, thanks to all for your continued help! Very much appreciated.