Can someone tell me how to advance the idle on my 1991 Johnson 115 HP motor? The motor shuts down after idling more than a minute or so. Runs fine if I advance the throttle.
That almost sounds like its loading up. Tell us a bit more about your rig. When it does idle, what rpm is it at before it dies? What spark plugs? What oil and what ratio? Does the idle improve if you tilt the motor up slightly? Does the motor sit deep in the water 9like on a bass boat)? have you tried a decarb job lately?<br /><br />I know, I know -- its too early for all these questions!
Did the engine turner spray and new spark plugs (NGK B9HS) this past weekend. Improved things somewhat, but it is not as it should be. This is original equipment on a center console boat (17' Grady-White) so it is not sitting down in the water. Since I purchased new in 1991, I have run nothing but mid-grade gas and Johnson oil. I change the plugs every 100 hours and spray tune every 50. It could have a carbon build up problem but I would be shocked. The motor has VRO Oil Injection. Sorry I didn't record what the idle was when it shuts down but it is lower than normal.<br /><br />Thanks in advance for you help.
Lets get some different plugs in it first. Use the Champion (Q)L77JC4's. You could use the QL78C's but I prefer the cooler ones. <br /><br />The motor should idle in gear at 750 or slightly less. If you need to adjust it remove the throttle cable and release the cam follower (roller). Then adjust the screw in the throttle arm. Reposition the roller and center the throttle cable.<br /><br />It may be a good idea to check compression while we're there.<br /><br />Good luck!
I'll try the plugs first. Any specific reason why you would change brand plugs? The motor came with Champions. I switched brands a couple of years ago when it came back from the repair shop with the NGK's. I didn't notice any difference it the performance at that time. I have no idea how many hours this motor has on it. I would guess well in excess of 2500. I expect it to crap out any day but it just keeps on humming. Nothing on it has been rebuilt.
The OMC's were designed around the burning and heat characteristics of the Champion plug. Just like the Mercs and Yammies were built to use NGK's.<br /><br />Has the motor been sitting for any length of time?<br /><br />2500 hours is not unusual for a well maintained and well set up 2 stroke outboard. You should expect many more hours of use. Lets get a compression check to establish a baseline.<br /><br />Good luck!
It had not been used for a couple months, however, its gets used pretty regularly year round. Had a compression check done last year and the mechanic said it was great considering the age of the motor. I'll try to have another one done as soon as possible.
