Need help adjusting Idle on 70hp Johnson

Parrot6909

Seaman
Joined
Dec 29, 2002
Messages
69
I have the shop manual in transit (just bought the boat on Friday).....The motor is a 1983 70hp Johnson......I have the motor in a 80 gallon barrel (not a big fan of using the flusher ears)..Started it up, and the idle is ~1500 rpm's and higher as it gets warmer, didn't leave it on for that long maybe 5 mins....I took off the cowling and played around with the throttle arm (if thats what its called..) got it down to around 600 or so. I shut the motor down after letting it run for a bit at the lower rpm's.....Started it, wanted to see if the fast idle lever worked, sure enough, went back up to 1500, pushed it down to be at slow idle and it doesn't go back unless you manually do it.....Need to know how to fix that.....happens if its in gear too, I shut the motor down and watched what the throttle arm did when i put it in gear, it doesn't move till about 3/4 throttle, then it gets really tight from 3/4 to full.......<br />I am trying to be descriptive here, not really sure how to fix it without the manual (this is my first boat that I have owned, have had boats thru my parents for years and years, but I don't have the money for the mechanic and I also find it satisfying to work on it myself......) So....if anyone can help me fix this, I would greatly appreciate it........No shop manual till Friday and want to go out on the water over the next day or two if possible....Thanks!
 

The Marine Doctor

Commander
Joined
Jul 25, 2003
Messages
2,177
Re: Need help adjusting Idle on 70hp Johnson

Either your throttle cable is broken or something is not right in your control box.<br /><br />You can though try an adjustment back on the engine where the cable comes in there is an adjustment barrel. You can turn this Black plastic piece. This will allow you to tighten the cable.<br /><br />TMD
 

Skyhigh

Petty Officer 2nd Class
Joined
Jul 25, 2003
Messages
131
Re: Need help adjusting Idle on 70hp Johnson

Thanks for the info doc.<br /><br />My 60 hp does the same thing....
 
D

DJ

Guest
Re: Need help adjusting Idle on 70hp Johnson

Parrot,<br /><br />Sounds to me like your cables are binding.<br /><br />Does the engine return to idle with the throttle cable disconnected?
 

Parrot6909

Seaman
Joined
Dec 29, 2002
Messages
69
Re: Need help adjusting Idle on 70hp Johnson

Haven't tried disconnecting them yet....Its really odd......The throttle works when shifting, i.e. if i put it in forward, it moves the throttle arm, but when i use reverse or the idle, nada.........
 

Parrot6909

Seaman
Joined
Dec 29, 2002
Messages
69
Re: Need help adjusting Idle on 70hp Johnson

Tried tightening the discs....no luck.... if i disconnect the cables and throttle goes back to normal, does that mean the cables are shot?
 

The Marine Doctor

Commander
Joined
Jul 25, 2003
Messages
2,177
Re: Need help adjusting Idle on 70hp Johnson

Your cables might be stretched. OR something is wrong in the box.<br /><br />TMD
 
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