1978 85 hp johnson carb questions...

[relocyo]

so i found out today the motor i just bought has 2 different size carbs on... so the question is can i put a pair of 1977 johnson 115hp carbs on a 1978 johnson 85 hp power head? ive kinda looked around but have had no success in finding that info... thanks... i have no clue lol... stamped on block is #85ML78C

 

[emdsapmgr]

Re: 1978 85 hp johnson carb questions...

Yes you can. Your 85 block is a small bore powerhead, at 92 cubic inches. The 115/140 is a larger bore powerhead at 99.6 cubic inches. The 115's and 140's use larger carbs to make more hp. You may find that the 115 carbs will work just fine as is, but don't be suprised if the engine overfuels just slightly on top end. You may have to go down a couple of main jet sizes for optimum performance. Overall, you should see a performance increase after the swap. I ran a set of huge 1 5/16" carbs from an early 125 on a small bore 85 years ago. They worked great after I spent a couple of weekends rejetting. Picked up about 250 rpm-enough to have to up the prop pitch.

 

[relocyo]

Re: 1978 85 hp johnson carb questions...

wow thanks for the advice... the only reason i was asking about the 115 is because their are a pair on craigs list near my home. if maybe you know what other carbs would fit on there that would be great for me too. im really just trying to get this motor to run and im not worried about any extra performance necessarily but when i search the entire intternet for "1978 johnson 85 hp carbs" there arent ever ANY hits so i feel stuck. and i dont really have the knowledge to "rejet" them either. thanks for any other help you can give me in advance! youve been very helpful thus far...

 

[relocyo]

Re: 1978 85 hp johnson carb questions...

and actually. that was kinda he prob i had on the carbs i was running... bogs down at WOT but the 2 carbs i have are 2 different sizes... how much does that matter?

 

[emdsapmgr]

Re: 1978 85 hp johnson carb questions...

It can make a difference, esp if the other carb is larger and is jetted for a larger engine, like a 135. That carb could create a bog situation till the airflow thru the carb increases with rpm. It could also negatively affect very top end, too.

 

[emdsapmgr]

Re: 1978 85 hp johnson carb questions...

It can make a difference, esp if the other carb is larger and is jetted for a larger engine, like a 135. That carb could create a bog situation till the airflow thru the carb increases with rpm. It could also negatively affect very top end, too.

 

[relocyo]

Re: 1978 85 hp johnson carb questions...

so how do i fix that? the other carb is only slightly bigger (there at my buddies shop or i would have exact specs.) or should i just keep looking for a new one or set... or is rejetting them an option like you had stated before.... im trying to go as low cost on this as possible... and do it myself...

 

[glassmaster68]

Re: 1978 85 hp johnson carb questions...

Imagine one cyl going wide open and the other at half power,the half power working against the other wide open one,robbing its power,THEY NEED TO GET EQUAL FUEL

 

[relocyo]

Re: 1978 85 hp johnson carb questions...

ok so i just got the specs. one is a 1inch d-5 #323302 and the other is a 1 1/16 d-6 #323352... i mean one sixteenth of an inch is gonna make me have to buy all new carbs for this thing? please tell me thats not true... i can deal with not getting to WOT as this is just a little 15 footer and extremely light....

 

[emdsapmgr]

Re: 1978 85 hp johnson carb questions...

One alternative is to find just one used carb, either a 1" or a 1 1/16." Buy whichever you find first and go from there.

 

[relocyo]

Re: 1978 85 hp johnson carb questions...

thanks everyone for the responses... i just bought a new pair... got a great deal sooo... and didnt want to burn a piston.... fresh water carbs too!!! thanks again... i think it will be worth it... the way my buddy put it is "your gonna spend what you spent on the carbs one day having to get the boat towed home" i LOL'd

 

[pilotboyle]

Re: 1978 85 hp johnson carb questions...

FYI: I've got carbs off a 78 70hp Johnson if anybody needs them. I'll take $100 for carbs. Also have stator, ignition, etc. (336) 414-2522 Doug