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carb jets 2003 40 hp

G

greenbomb

Member
On my 2003 johnson bombardier j40plstd why is the main jet( 048) in the fuel bowl smaller than the the intermediate jet (056) in the cover ???
My factory Part manual shows just the opposite . Bigger main and smaller intermediate . I have had this 2003 boat since 2007 and it really never idled right . So i rebuilt the carbs , new floats etc. but did not remove the main jets for fear of hurting them , but the intermediate jets are .056. still runs the same . can't get the idle to come up enough to be reliable docking. On a pontoon 5800 , 15 mph

The internet ( marineengine , and others ) show small main and big intermediate But my factory manuals show big mains in float bowel and smallintermediate . I would think the factory is correct or some paper pusher typoed the manual and that someone rebuilt the carbs before and mixed up the jets. Reeds are like new. Always fresh non alky gas , Rayco water filter , use star fuel stabilizer , Yamaha ring free . So after 355 hours on the meter and all these years i am trying to make this right thanks to Wohan and extra time on my hands. Course i will do social distance

Need some help guys starting to think my 72 plus age is messing with me
All suggestions greatly appreciated
Thanks in advance. Norm in Arkansas
 
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What goes through the jet in the float bowl ?----Is it fuel ?---------And I must ask , what goes through that jet in the cover.-----Is it air ??------I must also ask as to what other trouble shooting you may have done if any ?-----Just maybe it is not a carburetor problem.
 
someone rebuilt the carbs before and mixed up the jets​
Click to expand...
Jets are different physically and cannot be mixed up in location/placement.... A 40HP uses .048 main and .056 intermediate, 50 HP are different.
can't get the idle to come up enough to be reliable docking. ​
Click to expand...
Intermediates have nothing to do with idle...totally different circuit controlled by the adjustable needles. Carbs have to be set in the water or barrel. Cannot be done on muffs.
 
Racerone and Fastbullet . thank you '
You are both right in all accounts fuel in the bowel , air in the cover and approx .o60 top carb and .055 bottom carb intermediate jets. did not check main jets but will order new jets and a float guage and try again . Looking at my notes i have a 12 1/4 3 blade prop and with just me aboard i turn 5400rpm with a checked tach and 20 mph on the gps . Been following you guys with the GAP guy and scored bores. Will get a new head gasket and check the bores . one compression is 15 psi down. Changed all the rollers and set clearances and linkage at reference marks by the factory manual . Turning in the idle screw timing advance does not seem to help increase idle speed. Its about half inch out from full in and it does increase the initial timimg . Should i screw it all the way in?? TOO much roller clearance? Full throttle has the butterflies open . . boat is in the water and i use a hand held tack to set the idle screws to highest reading in gear. Just dumped the boat gas in my ruck and put in fresh premium with Yamaha ring free . 1 0z in 10 gals. YES truck still runs. As its on a slow pontoon i spend most of my time in the 2000 range, maybe i should go out and run it hard? The rollers were all bad and the timing linkage rod was wound in a bit. Initial timing is at 4 degrees now but it still seem to run the same. Floats are not upside down.. Has not had a hard life since i have had it. When your out cruising , looking and bulling there is not much use for 15 mph . It just makes for a hard drink spilling ride > Wives hate it. Oil injected omc $$$ semi oil. Thinking i better pull the head .Unless you guys work you magic . All suggestions welcome.

Thanks again , Norm i arkansas
 
Thats what i was thinking mr faztbullet after reading what GAP went though and the fact that timing linkage was very short. Anyway to check the exhaust ports for stuck rings??
Maybe a bigger dose of ringfree? LOL

Thanks again
Norm in Arkansas
 
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I also forgot to say that pinching off the primer lines with the engine running does not help and i replaced all the fuel lines using Bombardier part numbers and install the lines using tight fitting spring hose clamps . Not that the old ones were bad , but newer is better
 
Faztbullet
just some FYI . Got my new jets and they are both 1/4 -20 and look alike so they will interchange ! Must have been a cost saving feature . . Correct part numbers # 56 0318684, # 48 0349356 . NOW trying to figure out why my factory parts manual says the 056 is the main and the 048 is the intermediate? Thinking the 2003 factory manual is a misprint and might have had a retraction or recall .
You guys are really appreciated
Norm in Arkansas
 
Thanks you Mr Faszbullet.
I was wondering my my factory 2003 parts manual says just the opposite . Thinking it was a misprint i downloaded 3 other paid websites of the manual that all said 48 intermediate and 56 main . must all been copies of my factory manual., Fake News , never retracted. Looking at the same carb in other years i cam,e up with your jetting information . Im going with Yours.
Thanks again your help and time in this matter is Greatly Appreciated
Norm in Arkansas
 
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