Logo
FULL SITE MENU

Carburator issues 1980 70hp

T

toss42

New member
My 1980 70hp 3cyl johnson outboard will idle perfect,will idle when engaging forward and reverse,when in the water but when go to give her a fair amount of speed it sounds as if she is only running on one cylinder.after observing with the cover removed i noticed that the carb rods that connect the first and third carb has a spring located in the center that is attached to some sort of (solenoid)??? That has a piston that suppose to pull these rods to open and close carbs(i assume).its doesn't seem to be doing anything,that is, this piston with the spring attached to it and the carb rods.this outboard is electric start.
 
Re: Carburator issues

With the cover off, key on,(engine not running) hit the choke and watch the solenoid. The solenoid should pull choke plates on carbs closed.
On the running problem, these engines will idle pretty good on two cylinders. I would check spark and compression, if they are ok it might be time for the carbs to be overhauled.
 
Re: Carburator issues

daviet,could it be that the solenoid itself is gone.when I had her in the water,and engaged in drive(foreward)I went back to the motor and manually pulled down an the carb rod that connect the upper and lower carbs,(rod that has the spring connected from the solenoid)and all three carbs kicked in and she wokred perfect.I burned 3/4 tank of gas before I stopped, thinking that it might be crap in the carbs because I just changed the head gasket and water jacket gasket.Put her up and the next day went fishing and the same thing again.Pulled the rod and again, worked perfect until I stopped or slowed down.???????
 
Re: Carburator issues

daviet,I hit the choke and the solenoid did push the carb rod up.(with a clicking sound)Still confused why carbs works when pushing the rod manually.???? If I need to overhaul carbs,will I need a complete carb kit for each one(carb)?
 
Re: Carburator issues

If I am thinking correctly, when the solenoid actuates it should pull the plunger into the solenoid and close the choke plates, when you release the choke switch the plunger should release and the choke plate goes to the open position.
Yes, 1 kit per carb.
 
Re: Carburator issues

I don't think there is a written standard for compression. As long as the cylinders are above 120 psi, and within 10% of each other you should be good.
 
Re: Carburator issues

your carbs worked when you pushed the rod because, you were getting lest air into the carbs,making them rich instead of lean. take a spray bottle and put 50:1 gas/oil mixture in it. start the motor after it warms up, spary the mixture into the top carb, if the motor speeds up the carb was running lean, if no change the carb is set right, if it chokes it down the carb is too rich. do this with all three carbs and set them as you go and the carbs will be set.
 
Re: Carburator issues

compression doesnt have to be over 120 as long as they are equal and a reasonable number they will be fine
 
Re: Carburator issues

i stand corrected, Thats what I get for not looking it up. You can still use the spray bottle to find the carb that is lean or rich so you know which ones needs more cleaning.
 
Re: Carburator issues

Thanks guys for the info. I will use the spray bottle.This situation was getting very confusing.When you can push the carb rod and the motor works perfectly, its confusing to think that it could be the spark or compression,especially running her close to 40 mph up to 3/4 tank of gas in one continuous run on the lake.To set things straight what your saying coueytwo is that if the carbs speed up or choke they need cleaning.Only if they stay normal their good. I was also thinking that the solenoid wasn't activating enought to pull the rod open.
 
Re: Carburator issues

yes, the spray bottle is the way to check the carbs as you stated. don't worry about the choke systems right now, if you can start the motor and keep it running, use the spray bottle to find the lean carb. you would only use the choke to start the motor and to keep it running until it warms up. You would not use it when running the motor on the lake. what the choke is doing is getting more gas to the motor and less air. so if the motor runs better with the choke used, then it is running lean.
 
Re: Carburator issues

coueytwo my outboard is electric start so therefore the choke is on the key(ignition). I only use it to start.Also I forgot to mention that when the motor flush muffs is on her in my driveway she works perfect,it only happens when I put her in the water.??? Sorry about that. Not sure if this changes the whole situation.When I give her full throttle(in the lake) the motor seems to really suffer and the engine starts to really vibrate.Just can't get the power,until, like I mention,I go back and remove the cover and pull the rod that the solenoid is hooked to.??? This rod swivels on the upper and lower carbs with the solenoin spring attached to the center of this rod which I think operater the middle carb.??? It's difficult to explain,I'm not a mechanic.Every piece of advise really helps from anybody on this site.Thanks.
 
Re: Carburator issues

this is because there is the back pressure from the lake when it is in the water
no pressure when it starts up on land
 
Re: Carburator issues

Thanks guys,I will rebuild the carbs as you all say,then I will get back with the results.What ever it takes will be alot less expensive than a new 70hp Johnson.Until then,take care.
 
Back
Top