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Outboard Carb Question

dingelbarries

dingelbarries

New member
Ok stupid question time here. I have a 1978 115 Hp Johnson on my trimate. In this model and year the v-4s all had all the same part numbers for every component, except the carbs. Is it possible a set of 140Hp carbs can be put on my 115 motor to get 140 horse? Would anything else need to be changed (intake etc)? Does anyone know the part numbers for the 140 HP Johnson carbs? I realize if I wanted a bigger motor I should just put one on, but I am kinda attached to the lighter v4s. I know all the super speed freaks would just ditch a little 115 but hey I am getting 54.8 MPH (GPS) with a 21 pitch prop (RPM limited). I have a 24p raker and a 6 inch jack plate in the mail right now, according to what numbers everyone else has posted here I should get in the low 60s. I live in an area where a 45MPH speed limit is enforced on 3 of the 8 lakes close. Dont need 70+. Thanks in advance for anyones input. :confused:
 
I don't think bigger carbs would help. Like any engine you would have to change timming and compression. Too much timming will blow you engine. I will take a dependable outboard over a few extra HP's.
 
The main difference is a 140 will have different exhaust porting to match the increased air flow from bigger carb. It may also have a different compression ratio. Changing the carbs alone will probably make it run worse.
 
Thanks, fellas. I got a chance to talk to a friend who owns a motorcycle shop lastnight, he said basicly the same things. The carbs and intake along with heads. He said the crank and piston assembly were probably the same in the 115 and the 140,(thus the same part#s) but the heads were diffrent, intake would be diffrent too, but he wasnt sure about the exhaust on an outboard motor. Just have to se where the prop and jack plate get me and go from there. I really like the motor, it has run perfectly, and gets decent fuel economy.....maybe should leave well enough alone and look for a 140 of the same vintage to "hot rod" a little......
 
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