carb adjusting 1981 90hp v-4

[81_chapparel194]

ok its a 1981 rude v4 90hp and i am trying to figure out how to richen the carbs out to give it a little more fuel at take off. i read somewhere that my engine may be a fixed jet and non adjustable. i have had the carbs off several times cleaning rebuilding etc and never seen an air/fuel mixture screw like on cars/motorcycles and other small engines. so is it possible to adjust the air/fuel mixture on this motor with out changing jets?

 

[Rapio]

Re: carb adjusting 1981 90hp v-4

Your carbs will not have adjustable mixture. Why do you need a richer mixture @ "take off"? If the carbs are correct and the timing is advancing properly you got all there is for now. Try Evinrude parts diagram and list for carb online. It may show jets which will upgrade you (maybe) to a 100 or 115 HP with all else the same. Instead of upgrading HP I put an after market anti cavitation plate on and there is also 3 holes forward (i.e. toward the gear box) one each prop blade that can be drilled to avoid cavitation on sudden full throttle. I can't remember where I found this, but it all improved performance for waterskiing.

 

[emdsapmgr]

Re: carb adjusting 1981 90hp v-4

The jets that come in the carb from the factory are set. Their engineering dept spec'd them out to make 90 hp with the throat size of the carbs on the engine. If you oversize the jets slightly, it'll overfuel and it may not run as well. Your carbs have 3 jets for each carb throat: idle jet, mid jet and high speed jet. During overhaul, did you remove all the jets for a visual inspection? Use a Gumout type product to clean the carb passages?

 

[81_chapparel194]

Re: carb adjusting 1981 90hp v-4

The jets that come in the carb from the factory are set. Their engineering dept spec'd them out to make 90 hp with the throat size of the carbs on the engine. If you oversize the jets slightly, it'll overfuel and it may not run as well. Your carbs have 3 jets for each carb throat: idle jet, mid jet and high speed jet. During overhaul, did you remove all the jets for a visual inspection? Use a Gumout type product to clean the carb passages?

yes removed,soaked and cleaned all orfices and passages. the reason for wanting to richen up is because it wants to bog down on acceleration from idle. tried many different things from fuel lines to rebuilding carbs. when it bogs out i can bump the key in for the primer and it takes off. so it tells me its a fuel problem and since everything from the fuel tank leading up to the carbs have been replaced or either verified working correctly then i think its a lean fuel problem. i read a post on here and he had same exact issues and symptons as me and his was a lean problem and maybe a prop issue as he changed the prop during the process of richening the fuel. maybe i should try my prop although that prop has been running on it for years even before i got it. and it had the problem when i bought it. and yes compression has been checked and all were in specs. around 110 per cylinder if i recall right.

 

[81_chapparel194]

Re: carb adjusting 1981 90hp v-4

Your carbs will not have adjustable mixture. Why do you need a richer mixture @ "take off"? If the carbs are correct and the timing is advancing properly you got all there is for now. Try Evinrude parts diagram and list for carb online. It may show jets which will upgrade you (maybe) to a 100 or 115 HP with all else the same. Instead of upgrading HP I put an after market anti cavitation plate on and there is also 3 holes forward (i.e. toward the gear box) one each prop blade that can be drilled to avoid cavitation on sudden full throttle. I can't remember where I found this, but it all improved performance for waterskiing.

during take off it wants to bog down and i can push the key in for the primer and it takes off. or either i can run fast idle for a few minutes then take off. this happens more frequently when engine is warm and not cold. almost seems like a cold start but it actually runs better on a cold start then a warm start. so im thinking the fuel is lean and i need to put a little more raw fuel to the air mixture.

 

[emdsapmgr]

Re: carb adjusting 1981 90hp v-4

You could try to fatten up the mids a little and see what happens.

 

[Rapio]

Re: carb adjusting 1981 90hp v-4

Have you checked the filter (screen) in the fuel pump on the engine and do you have an inline throw away fuel filter that is due for a throw away. Also when you advance to full throttle with engine not running check that the spring loaded timing advance lever on the engine moves forward smoothly in relation to the carb lever. The ring under the fly wheel is inclined to gum up over the years and timing advance is restricted. Also: Consider a cold engine usually would require a richer mixture and a warm engine leaner. Remember the auto matic and manual choke for starting a cold engine. You might try having someone pump up the fuel squeese bulb while you advance the throttle on the water. Good luck.....hard to trouble shoot online

 

[81_chapparel194]

Re: carb adjusting 1981 90hp v-4

You could try to fatten up the mids a little and see what happens.

ok i will bite.. what exactly does this mean? slightly bigger middle jets??

 

[81_chapparel194]

Re: carb adjusting 1981 90hp v-4

Have you checked the filter (screen) in the fuel pump on the engine and do you have an inline throw away fuel filter that is due for a throw away. Also when you advance to full throttle with engine not running check that the spring loaded timing advance lever on the engine moves forward smoothly in relation to the carb lever. The ring under the fly wheel is inclined to gum up over the years and timing advance is restricted. Also: Consider a cold engine usually would require a richer mixture and a warm engine leaner. Remember the auto matic and manual choke for starting a cold engine. You might try ha i ving someone pump up the fuel squeese bulb while you advance the throttle on the water. Good luck.....hard to trouble shoot online

yes i have checked the screen.. clean
no i dont have any other fuel filter inline.
yes the timing advance works fine. even did a link n sync
my boat only has electric coke. push the key in. actually it is a primer no choke butterflies in carb. push key in and the "primer" sprays a mist of fuel into the intake.
tried the fuel bulb its hard after a few pumps and stays that way all day, but re pumping doesnt affect it while throttling up. tried that already. as said earlier have checked/replaced everything fuel related from tank to intake manifold. really about the only thing i havent checked/adjusted is the fuel/air mixture. unless there is a vacuum leak somewhere that i have overlooked. new gaskets between carbs and intake and between carb and air silencer/filter cover. checked compression, spark test with gap tester, all electric for fire. and as said before its worse after engine warms up. but is evident while cold start also. just not near as bad when cold. here is a routine i can do to take off. back boat off trailer (cold) idle over to dock or take right off gets up on plane fast. ride for a while dock boat for 5 min get back in and fire it up and idle out to wake zone drop the throttle and it dies. fire back up idles perfect drop throttle and it bogs. if i am fast enough i can bump the key in to "choke" but remember i dont have choke its a primer, then throttle up semi fast boat goes up to wot fairly decent. then runs fine AT wot until i dock again and it starts over. and here is ANOTHER method that gets me past that stage. fire up boat run fast idle lever up 3/8 to 1/2 way for maybe a minute or two then ease back to idle position then drop the throttle and it will shoot off like a rocket.

 

[wayneo99]

Re: carb adjusting 1981 90hp v-4

you say you keep pushing in choke to avoid the bogging. thats means the jets are not allowing the enough fuel to flow through them.
you have a fuel restriction somewhere and a lean condition which can cause a piston and cylinder wall damage.
I would go back and look at the carb float levels and jets.
also check all gaskets for vaccum leak but if it idles well it prob not that.

those carbs are the 1 inch size correct? with 2 fuel jets? and no air jets right?

 

[emdsapmgr]

Re: carb adjusting 1981 90hp v-4

Does the engine run fine at WOT?

 

[81_chapparel194]

Re: carb adjusting 1981 90hp v-4

you say you keep pushing in choke to avoid the bogging. thats means the jets are not allowing the enough fuel to flow through them.
you have a fuel restriction somewhere and a lean condition which can cause a piston and cylinder wall damage.
I would go back and look at the carb float levels and jets.
also check all gaskets for vaccum leak but if it idles well it prob not that.

those carbs are the 1 inch size correct? with 2 fuel jets? and no air jets right?

carb floats are properly adjusted. or were last inspection checked that numerous times. replaced all gaskets where air could intrude. and yes it idles perfect. and runs at WOT fine. it just bogs during acceleration. i figured it was fuel but i know that carbs are clean. i have pulled them several times and cleaned and soaked and blew light compressed air thru the passages. and i believe the carbs are 1-1/8 or either 1-3/8 (not sure i know its 1-?/8 positive.) and i believe my carbs have 6 total orfice jets 4 in the lower plate behind each screw and two in the upper portion of the carb throats. one in each throat. hmmm come to think of it are all of those the same orfices size? because when i removed them to soak and clean i removed all of them and and soaked them together i wonder if they are different sizes if i put them in the wrong place??? :facepalm:

 

[81_chapparel194]

Re: carb adjusting 1981 90hp v-4

Does the engine run fine at WOT?

engine runs perfect at WOT or as near perfect as i can tell.. no hiccups or stalling.

 

[emdsapmgr]

Re: carb adjusting 1981 90hp v-4

I doubt the engine is starving for fuel if it runs WOT just fine. It could even be the wrong jet. That could cause bogging at midrange. Back to square one: pull all the jets out of the carbs. Visually inspect them and double check the stamped size of the jet vs the original factory parts catalog. See the factory parts diagrams here: epc.brp.com for the jets/sizes. The mains are .065, the mids are .029, the idles are probably .034. If, during your re-assembly, you were not aware-the idle and mid jets are the same thread size (8/32) and can inadvertantly be mixed in the carbs. That can cause the running issues you have. (you can't get the mains in the wrong position.)

 

[81_chapparel194]

Re: carb adjusting 1981 90hp v-4

I doubt the engine is starving for fuel if it runs WOT just fine. It could even be the wrong jet. That could cause bogging at midrange. Back to square one: pull all the jets out of the carbs. Visually inspect them and double check the stamped size of the jet vs the original factory parts catalog. See the factory parts diagrams here: epc.brp.com for the jets/sizes. The mains are .065, the mids are .029, the idles are probably .034. If, during your re-assembly, you were not aware-the idle and mid jets are the same thread size (8/32) and can inadvertantly be mixed in the carbs. That can cause the running issues you have. (you can't get the mains in the wrong position.)

ok i just realized that could be the problem as i was typing that last message. ok i believe the idles are located in the bottom plate behind the UPPER drain screw. is that correct? and where are the mids located? are they the ones in the upper part of the carb throat? kinda angled downward a bit? or are the mids located behind the lower drain screws in the lower plate? i found a parts diagram online but it just calls them orfices and doesnt specify idle or mid or main.

 

[metriccrescentwrench]

Re: carb adjusting 1981 90hp v-4

i found a parts diagram online but it just calls them orfices and doesnt specify idle or mid or main.

Are you looking at the diagram at shop2.evinrude.com ? While it doesn't call out whether it's an idle, mid, or high speed jet they do at least show the position of each jet and call out the size for you, which might get you on the right track.

By the way, I've got that same engine on my 2nd boat and it's been great (once I got it fixed up from a neglectful previous owner).

 

[81_chapparel194]

Re: carb adjusting 1981 90hp v-4

Are you looking at the diagram at shop2.evinrude.com ? While it doesn't call out whether it's an idle, mid, or high speed jet they do at least show the position of each jet and call out the size for you, which might get you on the right track.

By the way, I've got that same engine on my 2nd boat and it's been great (once I got it fixed up from a neglectful previous owner).

no i was actually looking on the brp website but i know the mains are behind the bottom screws and idle behind the upper screws so it only leaves the upper jets in the throat as the mids. i cant believe that i fubbed up and didnt pay any attention that they were different size jets. as many carbs as i have torn apart and re assembled. although this is my first outboard. ya know had the boat not had carb problems to begin with i would have caught this sooner. but when i bought the boat the carbs were gummed up from old gas sitting. d'oh i had a brain fart. will disassemble them tomorrow and sort out the jets. hope to finally get this problem figured out. and by the way i love my rude. it has 90 strong hp. for such an old engine it is almost bullet proof. mine is the e90tlcim.

 

[metriccrescentwrench]

Re: carb adjusting 1981 90hp v-4

for such an old engine it is almost bullet proof. mine is the e90tlcim.

Yep, mine is the Johnson version, J90TLCIM, exact same engine. Sounds like you've got it under control, hopefully that will take care of it for you.

One thing I found with mine was that the factory specified plugs would start to foul after 6 months or so. Somewhere I read that there was a factory service bulletin stating that there was an alternate plug approved for this engine.... QL82C. I started using that one and it's great, I've had the current plugs in for over 2 years and when I checked them this winter they still look good.

 

[81_chapparel194]

Re: carb adjusting 1981 90hp v-4

Yep, mine is the Johnson version, J90TLCIM, exact same engine. Sounds like you've got it under control, hopefully that will take care of it for you.

One thing I found with mine was that the factory specified plugs would start to foul after 6 months or so. Somewhere I read that there was a factory service bulletin stating that there was an alternate plug approved for this engine.... QL82C. I started using that one and it's great, I've had the current plugs in for over 2 years and when I checked them this winter they still look good.

it had the oem # champions in it when i bought it but changed them to equivalant NGK plugs during the tune up. i like champion but for small engines i always prefer NGK plugs. no problems so far, in a years time. i may change back to the champion this season just to try them since johnny/rude reccomends them. usually mother (aka fctory) knows best. but i will note the new plug number for when the tune up is ready. thanks for that info

 

[emdsapmgr]

Re: carb adjusting 1981 90hp v-4

The idle air bleeds are the jets between the two throats on the face of the carb. Metricwrench is correct, just follow the factory diagram and insert the jets they way they appear on the exploded parts diagram.