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Switching carbs

J

JerryIke

Member
Can you switch a set of carbs from a 60hp to a 75hp Johnson. I know they are different by the numbers but what needs to be done to make it work?
 
You may need to change the exhaust tube what years are you talking about? If the powerhead is the same part number it may be just fine, racer will know better.
 
JerryIke said:
The 60 is an unk year....no numbers on it and is an Evinude But it has the VRO (which failed, hence the engine swap).
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I actually just swapped them anyway since so many things are the same. Runs fantastic now! The75 had been sitting awhile and I'm sure carbs were cruddy. I had rebuilt the carbs on the 60 last fall before winter storage. The75 now purrs and revs like a champ. Lake test this afternoon....
 
The block is different on the 75 hp has different porting. Make sure you are not running lean as the 75 block revs to 5800 I believe instead of 5500 for the 60.
 
The carbs don't have much in the way of adjustment screws. Do I adjust lean/rich by the one screw at the top of the carbs that is in the front?
 
I spent over 2 hours on the lake yesterday. I never shut the engine off during the whole time. I ran various speeds from idle to full throttle without so much as a burp from the engine. I believe I lucked out with the carb swap!
 
Keep an eye on the spark plugs, they should be a toasty brown on the electrode insulator. If they come out a powdery white your running too lean and will cook the pistons and rings. Tell us what the plugs look like.
 
kimcrwbr1 said:
Keep an eye on the spark plugs, they should be a toasty brown on the electrode insulator. If they come out a powdery white your running too lean and will cook the pistons and rings. Tell us what the plugs look like.
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I will look a little later and post pictures if anything "suspicious". If too lean, how to I rich them? I only see one screw for any adjusting. It is located in the face of the carbs. Currently the are screwed out 1 and 1/4 turn.
 
The slow jet is adjustable If the plugs come out white you can increase the main jet size. The high speed jets are normally in the bottom of the float bowl. Do you have pics of the cowl on the motor to establish the year and HP. And do you know the year of the new carbs and HP?
 
If the carbs came off a 56ci 60hp your good to go as these are a bigger bore...it may end up your a tad rich at WOT on a 49ci block. The high compression head on the 75hp will benefit from the slight fuel increase...
 
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