1993 120HP Idle Problem/Compression Question

[kjjack]

I've got a 1993 120HP V4 90V loop charged Johnson that just wont idle very well. After it warms up, it will idle well while I'm out on the water for a while. However, every time I take it out on the water, when I'm coming in to trailer it, it wants to die everytime I put it into idle, or when I try to shift from forward to reverse. (It's really a pain when your trying to back off when approaching the trailer and it dies)

Anyway, my questions are:
1) I'm going to do a compression check, what are normal compression numbers for my motor?

2) I'm wondering if I should adjust the fuel/air mixture screws on the carbs. My (stupid) question is, can I adjust these with the motor running and with the air silencer (cover) removed?

Also, I noticed one of my carbs is missing the slow-speed mixture screw. Could this be a problem with the idle?

 

[tashasdaddy]

Re: 1993 120HP Idle Problem/Compression Question

#1 you don't have any adjustable jets. all are fixed. #13 is slow speed #19 is intermediate speed (mid speed) # 15 is high speed. i think you idle speed is set low. the idle speed needs to be 650-750 rpms in the water and in gear. it will run fine on muffs, but in the water there is backpressure, on the exhaust, this causes the motor to stall when put into gear, because it cannot push the exhaust out. you can view diagrams of all you motor here- follow prompts.
http://shop2.evinrude.com/ext/index.aspx?s1=bf6ad09c53cead335fcfd8a6471c0f7f

 

[wavrider]

Re: 1993 120HP Idle Problem/Compression Question

Welcome to Iboats.

Great Forum here with lots of good experience and members willing to assist you on problems.

Compression? Usually 100 lbs with 10% variance between cylinders, your engine may be a little less as it is a looper, the experts may jump in and tell you a little more about it.

Not idling? Common problem with outboards, usually die to be stored or not run in a few months, gas goes bad, varnish and gum in the carbs, adding some fuel stabilizer will solve this problem, always add stabilizer when ever you fill up your tank with gas, helps prevent alot of headaches.

Going to need to rebuild those carbs, tery adjusting the idle forst on your engine you may be idled to low, keep it in the manufactures suggested tolerances, probaly around 650 to 750 rom in gear. Around 1000 rpm on muffs.

If the adjustment or if the idle is in the correct range according to manual. you do have a repair manual for your engine right? If not get one, it will save you hundreds of $$$ in the future on repair, if you perform your preventative maintenance this engine will serve you well for decades to come. Manuals available from your local dealer or online, get a factory manual, better specifics on details

rebuild carb kits can be purchased from this site.

 

[kjjack]

Re: 1993 120HP Idle Problem/Compression Question

Thanks for the help.
According to my manual (and verifying by looking at the carbs), my carbs have 4 mixture adjustments.
1. idle air bleed orifice screw
2. slow-speed mixture screw
3. intermediate mixture screw
4. high-speed fuel orifice

Also, can I run the motor with the air silencer off?

 

[Faztbullet]

Re: 1993 120HP Idle Problem/Compression Question

Yor are correct on your carbs. Certain model series came with different carbs in 92-94. The air needle works with the air idle bleed jet on this style. These carbs are not the best in the world and tricky to adjust to get a decent idle. The missing adjustment screw will cause the problems you describe and you should have a lean spit @ idle. When I rebuild these carbs I shut the air needle all the way off and install a #30 air bleed jet and engines idle really well this way. Your compression should be 100psi or higher. All compression guages dont read the same so any thing 95-120psi is good.

 

[kjjack]

Re: 1993 120HP Idle Problem/Compression Question

and the air silencer?

 

[Faztbullet]

Re: 1993 120HP Idle Problem/Compression Question

Not suggested as this is not the non restricted air box. Ok to do testing with it off.

 

[kjjack]

Re: 1993 120HP Idle Problem/Compression Question

so it should be ok to run it in the driveway with muffs on and air silencer off to adjust idle screws?

 

[kjjack]

Re: 1993 120HP Idle Problem/Compression Question

...

 

[Faztbullet]

Re: 1993 120HP Idle Problem/Compression Question

Cannot adjust on muffs. Engine must be in water with back pressure.If you havent fooled with them (idle settings) just count turns in and set the one that fell out to the same.