1988 35hp johnyrude carb info - pics if you have them

[hot-dog]

hi, im new to this forum. the reason i came here is because i need a little more information on a carb upgrade for my 83 25hp johnson. i have done allot of research on it and have found that the 1984 35hp is the the most similar engine to mine of all the 35. i have cross referenced part numbers for hours and found there to be no difference other then the carb only on the 84 model. its also a commercial long shaft so the lower unit is up to it and i my 10.5x14 4 blade should barely be deep enough if i spin it close to 6k.

anyways i plan on boring my carb to the right size and modifying it to accept mikuni or keihn main jets as im already familiar with tuning those types of carbs. the idle circuit should be ok so the main jet is all that needs to be tuned. so i would RELLY like to see some pics of an 84 35hp carb if you have them. anyone that has this model engine i would greatly appreciate if you could take a picture down the barrel or measure the bore for me. i mainly want to find out of the carb is just a direct through bore or if they leave some of the lip on it. the gaskets are the same part number for both motors so the base diameter is probably the same size, im thinking that lip is what restricts it down to a 25hp.

the last thing im curious about is how these carbs operate at part throttle vs wide open, there is no needle or anything to restrict the main feed. im thinking it must just work because the throttle blade is after the jet which would make it sort of vacuum referenced?

if you want to tell me its a stupid idea, go ahead, any input is welcome!

 

[hot-dog]

Re: 1984 35hp johnyrude carb info

Re: 1984 35hp johnyrude carb info

dang this forum moves fast...

no one has anything to say?

 

[tashasdaddy]

Re: 1984 35hp johnyrude carb info

Re: 1984 35hp johnyrude carb info

there is far more than just changing a a carb, porting, exhaust, etc, and a good way to muck up a good motor.

 

[TLL]

Re: 1984 35hp johnyrude carb info

Re: 1984 35hp johnyrude carb info

I did quick check of the block part numbers and the 25 hp and 30 hp are the same. The 35 hp is different. This indicates to me that there were mimimal changes (likely just the carb) between the 25 and 30. I believe that the 35 hp block has internal differences-porting etc... Also note that your gearcase really isn't heavy duty being a commercial, just an older style. The 30 and 35 have a much more efficient gearcase. Also how do you plan to bore the venturi of the carb, the brass tubes running though the center are not removable. Why change to another style of jetting? A variety of sizes of jets are available from any J/E dealer. It would be best to just find a carb off a 30 or 35. I agree with above, this is a good way to muck up a good motor.

 

[hot-dog]

Re: 1984 35hp johnyrude carb info

Re: 1984 35hp johnyrude carb info

ok i just realized i mislabeled the thread.. i meant to say 88. that must have caused some confusion!

i have done my research, and it only works this way from a 1987 25 to a 1988 35hp.

heres a list of parts that have the exact same part number between the two.

gear case - both 0393423
crankcase assembly - both 0396194
crankshaft - both 0328376
pistons - both 0392621
connecting rods - 0396194

i could check more parts but it seems pretty obvious that if all the major components are the same, its probably the same powerhead.

and like i said 1988 is the ONLY year 35 that is this way. in 87 the 35 was a detuned 40, and all the years below that the 35 was the same basic design as mine but the case/cylinders/pistons didn't match up so probably different bore/strokes. then 89 and up is the same as 86 and down.

now back to the carb, most of the time brass parts are just a press fit deal on carbs, is that not the case on these? i also had no idea different jetting was available, didn't see anything on the omc parts finder.

the other thing is these loopers run realy rich, and they aren't exactly fine tuned. jetting one right couldn't be too difficult.

 

[tashasdaddy]

Re: 1984 35hp johnyrude carb info

Re: 1984 35hp johnyrude carb info

it is your motor. do what you want with it. we do not condone it.

 

[hot-dog]

Re: 1984 35hp johnyrude carb info

Re: 1984 35hp johnyrude carb info

it is your motor. do what you want with it. we do not condone it.

did you read the above post?

can someone just post a pic of an 88 35hp carb, id like to at least see what the difference is.

 

[hot-dog]

Re: 1984 35hp johnyrude carb info

Re: 1984 35hp johnyrude carb info

i tried to get the brass tubes out... looks like its not possible. guess il just keep looking on ebay for a carb.

 

[fix_it]

Re: 1988 35hp johnyrude carb info - pics if you have them

Hello there. Some say that this can't be done... won't work right... whatever. I have a 1988 20 HP Johnson. I put on a 35 HP carb. HUGE difference. I have done the same looking that you did at the parts lists. The only difference in the 20 thru 35 HP is the carb and the intake manifold. The only difference in the 20 to 25 is the size of the hole on the intake. The carb is the same. Just ream out the hole and it's a 25. The difference in the 25 and 30 or 35 is a larger carb and larger volume inside the intake manifold. I just reused the 20 manifold and reamed it out to match the throat of the carb. I used a carb from a 1976 model 35 HP I think. The 76 carb was a choke type and the 88 was a primer type. I just removed all the choke parts (shaft, butterfly, linkage, everything). Then I drilled a hole in the carb for the primer nozzle from the 20 HP carb. No problems. I am using a 13 pitch prop. I have a fairly heavy boat and I run GPS about 30 MPH or so.

Good luck with the upgrade. Just make it easy on yourself and get a 35 HP carb. Preferably a primer carb, but don't walk away from a choke carb if that is all you can get. You can put the primer nozzle in it and it will work fine.

 

[tashasdaddy]

Re: 1988 35hp johnyrude carb info - pics if you have them

fix_it, you obviously are not the novice owner, mech.

 

[hot-dog]

Re: 1988 35hp johnyrude carb info - pics if you have them

Hello there. Some say that this can't be done... won't work right... whatever. I have a 1988 20 HP Johnson. I put on a 35 HP carb. HUGE difference. I have done the same looking that you did at the parts lists. The only difference in the 20 thru 35 HP is the carb and the intake manifold. The only difference in the 20 to 25 is the size of the hole on the intake. The carb is the same. Just ream out the hole and it's a 25. The difference in the 25 and 30 or 35 is a larger carb and larger volume inside the intake manifold. I just reused the 20 manifold and reamed it out to match the throat of the carb. I used a carb from a 1976 model 35 HP I think. The 76 carb was a choke type and the 88 was a primer type. I just removed all the choke parts (shaft, butterfly, linkage, everything). Then I drilled a hole in the carb for the primer nozzle from the 20 HP carb. No problems. I am using a 13 pitch prop. I have a fairly heavy boat and I run GPS about 30 MPH or so.

Good luck with the upgrade. Just make it easy on yourself and get a 35 HP carb. Preferably a primer carb, but don't walk away from a choke carb if that is all you can get. You can put the primer nozzle in it and it will work fine.

yea, i have no problem with porting the manifold. i really don't care what style carb i get, my primer is cooked and i keep fuel in a water bottle with a slit in the cap for manual cold start priming anyways.

another thing that has me completely baffled is the difference between the 30 and 35, i cant find any diference between the two? does the 30 just have a throttle stop in 88? other years arent this way but the 88 model 35 shows to have the same rods, pistons, crank case, intake manifold, exhaust cone, reed assembly, heads, and carb as the 30...

anyways, i measured that pee shooter out and the venturi measures out to a whoping 23mm! a 521cc 2 stroke fed by a single 23mm, no wonder it only makes 25hp! i assume the 35 carb is somewhere in the 32-35mm range.

 

[blimp]

Re: 1988 35hp johnyrude carb info - pics if you have them

yea, i have no problem with porting the manifold. i really don't care what style carb i get, my primer is cooked and i keep fuel in a water bottle with a slit in the cap for manual cold start priming anyways.

another thing that has me completely baffled is the difference between the 30 and 35, i cant find any diference between the two? does the 30 just have a throttle stop in 88? other years arent this way but the 88 model 35 shows to have the same rods, pistons, crank case, intake manifold, exhaust cone, reed assembly, heads, and carb as the 30...

anyways, i measured that pee shooter out and the venturi measures out to a whoping 23mm! a 521cc 2 stroke fed by a single 23mm, no wonder it only makes 25hp! i assume the 35 carb is somewhere in the 32-35mm range.

Don't mean to bump an old topic, but I am also curious as I have an '88 30hp Johnson. What IS the difference in the 30 and 35hp models?