Whats the difference between these 2 15hp carbs???

[BlackoutBill21]

Ok small back story... I have a carb... only 1 carb... it’s 15hp. Plastic top and bottom... 87-92 I believe

it’s on a motor... the type of motor is irrelevant at this point in the story..

now... according to brp parts catalog... 15hp longshaft Motor has high speed jet #55

and the 15hp sailboat extra long shaft motor has high speed jet #54

i need to know what jet I should use for my carb and motor setup....I really just wanna know what the difference in carbs /motors was for 15 long and 15 extra long that they would use different Jets.

I don’t have another option... I don’t have a 9.9 carb and I’m not spending 150 on a new/used carb

now the part of the story I hope y’all do NOT focus on...

this is the carb I’m using for my 9.9 Evinrude...
I bought it this way... some previous owner took this carb off what I believe was a sail boat.. original jet was #54

but my motor won’t run correctly and I’ve fixed a whole bunch of other issues... so I just need to know should I run the typical 15hp jet (#55) or the slightly smaller sail boat jet ( #54)

hope I didn’t lose y’all....

 

[racerone]

Perhaps you will not like this but , the problem has nothing to do with the wee difference in carburetor jets.------Trouble shooting is required to find the real problems.

 

[BlackoutBill21]

NAILED IT!!! didnt wanna know why my motor runs bad,.... just wanna know what the difference was between the 2 jets and carbs,,,,

now that thats out of the way... anyone?

for the record... the carb jet is part of the trouble shooting process

 

[racerone]

Can you provide the exact model # for a 15 HP extra long ( 10" extension ) sailboat motor ?

 

[BlackoutBill21]

according to brp parts catalog they dont make a 15 hp extra long sailboat motor.. only 9.9....

if thats true... where the heck did this carb come from??? it s100% 15hp... and it came with a 54 high speed jet... plastic top and bottom

 

[Newbie@boats]

If you’re so concerned about the jets being a 54 or 55 why not
just swap out the jets and figure it out? Since you don’t want to acknowledge the fact how such a tiny difference in jets will hardly make a difference in anything.

 

[GA_Boater]

hope I didn’t lose y’all....

Ya did. You've been troubleshooting this for a year but you don't want to know that the problem is. Have you looked for a #53 to throw in to see if it's the problem. Unlikely but you would eliminate the jet. Maybe grab a #50 to match the 9.9 spec.

https://forums.iboats.com/forum/engi...-carb-no-power

 

[tomhath]

How are you sure the carb is really a 15hp? Just because the previous owner said so doesn't make it one.

When you look through the carb's throat can you see a significant reduction in diameter? If so it's a 9.9 and the jet is wrong...wouldn't be the first time someone thought that changing the jet would magically give them 50% more power.

 

[oldboat1]

9.9 carbs are easier to find than 15s, probably because everybody wants to convert their 9.9 motors to 15. I would try looking for a 9.9 carb you can rebuild, preferably for your motor yr.. Make sure it's got the correct 9.9 jet for the year, or replace it with the correct one.

The Yachtwins came with a 15 hp body (larger throat), but a mid-sized jet. If you have a Yachtwin carb, you have a 15 hp body. If sticking with that carb for your 9.9, I would use the mid-sized jet. If that mid-sized jet was smaller for your motor model year, I would use the mid-sized jet for your motor year (some variation). For what it's worth, my 9.9 hp '83 and '85 Yachtwins run smoothly throughout the throttle range -- idle down well, if that is a consideration.

 

[BlackoutBill21]

If you’re so concerned about the jets being a 54 or 55 why not
just swap out the jets and figure it out? Since you don’t want to acknowledge the fact how such a tiny difference in jets will hardly make a difference in anything.

who said i wasn't concerned that it would make such a difference???
I have swapped the jet.. all three actually.. its ran like crap each time... again it was a simple question.. what was the difference... not why the engine runs bad.

 

[BlackoutBill21]

Ya did. You've been troubleshooting this for a year but you don't want to know that the problem is. Have you looked for a #53 to throw in to see if it's the problem. Unlikely but you would eliminate the jet. Maybe grab a #50 to match the 9.9 spec.

https://forums.iboats.com/forum/engi...-carb-no-power

I have all 3 jets... and same problem all three.. Yes its been a year... yes ive checked everything else... This time Ive fixed other issues and i'm almost done putting the motor back together... and before I put the carb on Id like to have the best shot at success so i figured Id ask to find out which jet would work best...

so now that ive explained myself at nausium again... the question was a simple one... difference between the 2 jets in the same carb....

 

[BlackoutBill21]

How are you sure the carb is really a 15hp? Just because the previous owner said so doesn't make it one.

When you look through the carb's throat can you see a significant reduction in diameter? If so it's a 9.9 and the jet is wrong...wouldn't be the first time someone thought that changing the jet would magically give them 50% more power.

previous owner never said it was a 15hp carb, i discovered that is what was on it.. the throat is large.. never gets reduced like the 9.9... its a 15hp carb.

 

[BlackoutBill21]

9.9 carbs are easier to find than 15s, probably because everybody wants to convert their 9.9 motors to 15. I would try looking for a 9.9 carb you can rebuild, preferably for your motor yr.. Make sure it's got the correct 9.9 jet for the year, or replace it with the correct one.

The Yachtwins came with a 15 hp body (larger throat), but a mid-sized jet. If you have a Yachtwin carb, you have a 15 hp body. If sticking with that carb for your 9.9, I would use the mid-sized jet. If that mid-sized jet was smaller for your motor model year, I would use the mid-sized jet for your motor year (some variation). For what it's worth, my 9.9 hp '83 and '85 Yachtwins run smoothly throughout the throttle range -- idle down well, if that is a consideration.

THIS!!! yes thank you! this HELPS!! Ive looked for a 9.9 carb but but nothing under 100 and Im low on funds but i will keep looking Thank you sir

also.. when you say 15hp body.. youre refering to the housing? or the crankcase engine itself?
engine tag says E10RLCCD

 

[juno pierrat]

to answer the question, one size makes little too no difference,,, had to do it on my motor , no difference

 

[racerone]

#55 has a calibrated hole 0.055" in diameter.------#54 has a hole that is 0,054" in diameter.------You would use grade 5 math to determine the difference in area.----Then go to grade 10 physics to calculate different flow rate.

 

[oldboat1]

Reference above to 15hp body was to the carb housing. If shopping for a 9.9 carb body, you want one that will match the choke rod, mix adjustment needle/knob, etc. That's why one to match the oem carb for your model number would be ideal (for fit). There's one out there somewhere. (How do you feel about parts motors?)

 

[Tim Frank]

I have all 3 jets... and same problem all three.. Yes its been a year... yes ive checked everything else... This time Ive fixed other issues and i'm almost done putting the motor back together... and before I put the carb on Id like to have the best shot at success so i figured Id ask to find out which jet would work best...

You are talking about 3 jets….then in the next paragraph only 2 ????

so now that ive explained myself at nausium again... the question was a simple one... difference between the 2 jets in the same carb....

You mean now that you THINK you have explained yourself.
I can understand and sympathise with your frustration that nothing you have tried works for you....and I can understand the frustration of everyone responding that you will not listen, will not answer simple questions, and have done everything BUT explain yourself clearly.....then get ticked at everyone for not telling you what you want to hear.
The difference between the 3 jets mentioned in the thread is less than 5%....as a reference, the typical jet for a 9.9 is a #34….almost ½ the size.

What you have as a carb/jet combo is really anyone's guess. But it is entirely possible that the carb you have will just not work with the jets you have when installed on a 9.9 HP……that seems to be what you are trying to do, but even that is far from clear.
As has been explained to you “ad nauseum” there is not enough difference in those jets to cause a total collapse in performance. Hence, there are other issues…..which need to be tracked down and eliminated by effective troubleshooting.
If you are trying to get 15hp from that 9.9, there are many other possible mods that could be required as can be deduced from the number of threads in here from folks who have started down the path looking for the Holy Grail and never get there.

JMHO, your results may vary, ......although not so far.

 

[BlackoutBill21]

Reference above to 15hp body was to the carb housing. If shopping for a 9.9 carb body, you want one that will match the choke rod, mix adjustment needle/knob, etc. That's why one to match the oem carb for your model number would be ideal (for fit). There's one out there somewhere. (How do you feel about parts motors?)

love parts motors! lol but people around here want like 400 for anything running or not.. I did see some steal bowl carbs on ebay for around 50.. i may go that route! this plastic carb is just too much hassle. Amd i dont even want 15hp just a solid running long shaft

 

[Tim Frank]

it’s on a motor... the type of motor is irrelevant at this point in the story..

I (AND I THINK MOST OTHER READERS/POSTERS) ARE LOST WHEN YOU MAKE A STATEMENT LIKE THAT.

You have a carb, with apparently zero provenance....and you want to swap it onto a motor that you will not identify.

As stated in post #17, how can anyone tell you what the difference in jets is....other than the obvious diametric difference, which is obvious.

Read the two threads below and consider that not only can you not really be sure what vintage your carb is, you are at the mercy of whatever "tuning" has been done by the original owner. You may have a "frankencarb" as a baseline....in my experience, carburetion is 3 parts engineering and at least 1 part witchcraft....some combinations "should" work, but simply do not.
If you have time, also search for other posts started by this guy. Many are exactly what you are dealing with. A 15 hp. carb on a 9.9 and it runs like crap. Go figure.

I would try and get my hands on a #35-#45 jet and see if there is a substantial change. That will give you a better benchmark. I would bet there is simply way too much gas getting through for the motor to function properly.

I would think that the vintage of the 9.9 that you are trying to re-engineer is way more important than the difference between the jets that you have. If you know model #, double check the jet spec for its OEM carb.

https://forums.iboats.com/forum/engi...1987-15hp-carb

https://forums.iboats.com/forum/engi...-over-3000-rpm