fast idle ?70hp Johnson 1994

[catface]

1994 johnson, new powerhead, still breaking engine in.10 hours with 50:1 mix. On cold starts engine fires up fine and after a few minutes rpm drop from 1200 to under 1000. however after runnin for a while and then restarting the rpm drops slightly in idle but not below 1000. how do you do the idle adjustment??

 

[Beaux]

Re: fast idle ?70hp Johnson 1994

Sounds like quickstart feature is working normally at cold crankup. It usually runs 1-2 minutes when cranked up and is cut off by powerpack by one of three situations; 1)timer of 1-2 min. expires 2)correct warmed temp reached (3) rpm limit reached @1200-1500.<br />Does your motor respond in this manner? *** The quickstart feature will always intitially turn on every time you crank the motor whether warm or cold. <br />Also- if you were to simply adjust the idle to lower rpm to compensate after running motor, then at initial cold startup, the motor would likely run at to low an rpm for smooth operation... maybe these other guys on the board can help suggest carb problems that relate to your motor's symptoms. Good Luck

 

[Beaux]

Re: fast idle ?70hp Johnson 1994

by the way, have you given it time after a "running for a while" start to see if it responds the same way as when it is completely cold?

 

[ob]

Re: fast idle ?70hp Johnson 1994

catface,You got a horsepower for that 94 johnson?10hp? 250hp?

 

[catface]

Re: fast idle ?70hp Johnson 1994

its a 70 hp johnson!on cold starts it functions perfect with a higher rpm 1200avg to after a minute or so down to below 1000 (800-900). runs excellent in the water. But when shifting into neutral after running its in a high rpm and stays there ie1200 you can even sense that it is high rpm. So I turn the engine off few min restart, goes instant start but stays at the high rpm 1200 and even after waiting a few mins, it does not drop down like it does on the cold start!so I feel when shifing at this rpm may be damaging in the long term. thanks for the response by the way<br />greatly appreciated!!

 

[Bear]

Re: fast idle ?70hp Johnson 1994

Seen this?<br />OMC Quick-start Info sheet:<br /> http://marinemechanic.com/site/page192.html

 

[ob]

Re: fast idle ?70hp Johnson 1994

catface , Sounds to me like the throttle cable and linkage maybe a bit sticky.Lube all points on linkage and if need be adjust top trunion nut in water after warmup to attain proper rpms.Insure your carb flaps are completely closing when throttle control is returned to nuetral.Also, check to see that the cam roller that rides on the fiber cam is aligned on center with scribe line and "just touching" when controls are in nuetral.There is a lock screw for this adjustment.

 

[fredmfl]

Re: fast idle ?70hp Johnson 1994

I have a repair manual for my '94 90 hp V4 Johnson and it sayes that you should use a 25:1 gas/oil ratio to break in your 70 hp engine for the first 50 hours. then 50:1.<br /><br />My 90 runs 1100 rpm idle also and they say to retard spark to slow it down. Or you can dfo a little diddy with the throttle cam follower pickup to help back off the spark when you throttle down. May need a little larger follower on your follower to bring it down more.

 

[fredmfl]

Re: fast idle ?70hp Johnson 1994

I have a repair manual for my '94 90 hp V4 Johnson and it sayes that you should use a 25:1 gas/oil ratio to break in your 70 hp engine for the first 50 hours. then 50:1.<br /><br />My 90 runs 1100 rpm idle also and they say to retard spark to slow it down. Or you can dfo a little diddy with the throttle cam follower pickup to help back off the spark when you throttle down. May need a little larger follower on your follower to bring it down more.

 

[clanton]

Re: fast idle ?70hp Johnson 1994

Needs a sync and link adjustment. At idle the throttle plates must be completely closed and the throttle cable should hold throttle lever against throttle stop. Idle rpm 600-700 rpms in water in gear boat moving. When everything is correctly adjusted, the idle can be move up or dowm by changing idle timing. Manual would help, then must match correct chapter to engine model.

 

[catface]

Re: fast idle ?70hp Johnson 1994

thanks for the response! I'll check the throttle and linkage and make sure I'm using the correct oil mix for breakin. my first step will be to get to the library and see if I can find the repair manual for this year, I'll post how things went when I get a chance to work on the engine after it stops raining again!!any response is still much appreciated though. cheers rich