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Idle speed Johnson V4

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fuzzbutt

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Got a '79 Johnson 100HP V4

Got a '79 Johnson 100HP V4 that has a slightly high idle. I have 1100 RPM in the water in gear or not. I should see 750-800 in gear.

I have 115 HP carbs on the motor right now and with my stock carbs I do not have this idle issue. I'd like to keep the larger ones but need to figure out a way to get the idle down a bit before I hurt the lower unit. I run a stainless prop so it is quite abrupt shifting into forward or reverse at 1100 RPM.

Should I change the idle jets a size or 2 up or down? They are 27's and 28's right now. I don't know if I need 29's or 26's.

Ideas?

Thanks in advance.
 
What fun would that be. Obviou

What fun would that be. Obviously my motor was in need of more air flow into the motor cause it runs much better on the top RPM ranges. Anything from 4000 on up to 5800 and it is much better than 1 inch bores that came with it. Everything else being the same I had a 400 RPM increase at WOT using the same prop.

I just don't want to waste $35 on a set of jets that are the wrong size.
 
"The 1979 100hp Evinrude was d

"The 1979 100hp Evinrude was designed to run properly at all rpms with the assigned carburetors. When it does not, something is amiss such as carburetion, ignition, compression, etc, which requires correction. I've never encountered a engine that suddenly developed a problem whereas it required more airflow unless said engine was being modified.

Years back, I had a few friends that installed 235hp carburetors on 150hp and 175hp engines in an attempt to increase their hp. They could never get those engines to run properly for some reason, whatever it was I refused to become involved.

However, good luck in your quest, I hope you find your answer."
 
I think I have a throttle shaf

I think I have a throttle shaft leak on the lower carb. there is a bit of up/down play in the shaft before it starts to turn. That might account for a bit of an air leak.

The motor seems to have woke up at the upper throttle range. I've run 2 cans of decarb thru the motor since May and also run BRP's fuel additive to ward off carbon issues. My motor was purchased used and I don't know much of it's history. I can tell that at some point in the past some sort of cylinder work was dine. I have excellent compression 145 on both RH pistons and 135 on both left hand pistons.

I'm going to look into the shaft bushings at the very least. I also have a bit of a problem with the throttle arm returning to the idle stop (though the carbs are at closed position) resulting in a bit of a timing advance. No amount of cable adjustment can get it to return to the stop on a regular basis.

I will likely put the stock carbs back till I can go thru the new ones with a fine toothed comb. They are 32 years old so anything is possible.
 
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