Idle Problems - 93 Mercruiser Alpha 1 5.0LX

[kburke1]

Engine runs smooth as silk during acceleration, top speed, and will idle ONLY when in gear and have to set the throttle lever just right. It will run smooth as low as 500-600 rpm "in gear" (according to tach) but seems to be the right idle speed if I could shift to Neutral. Shift to neutral and it sputters and dies. Would this most likely be throttle cable adjustment or carb needs adjusting? Has fresh oil & filter, new plugs, and new fuel filter. Thanks in advance for any advice. Will take it in for service after the holiday weekend if not something I can fix.

 

[waterone1@aol.com]

Re: Idle Problems - 93 Mercruiser Alpha 1 5.0LX

Is this boat new to you ? Did this problem just develope ? Other than adjusting the idle after some work has been done, it shouldn't just go out of adjustment. If you depress the "throttle only" lever on the control and give it a little gas, does it stay running then ? The quick answer to your question would be to adjust the idle screw on the carb so that it idles at about 650 rpms. I still think there is an underlying problem.

 

[kburke1]

Re: Idle Problems - 93 Mercruiser Alpha 1 5.0LX

I have had the boat for 3 years (93 Crownline 196 BR w/ 320 hours) and other than winterizing & de-winterizing, no service has been needed. The problem started at the end of last year. At first I passed it off as stale gas as it did sit for awhile at one point in between usage. This is when the problem developed. I did forget to mention I "can" depress the throttle only and just move it a little forward and get a smooth idle at around 600 rpm. It is only when I click the throttle lever into neutral that it stalls.

 

[Don S]

Re: Idle Problems - 93 Mercruiser Alpha 1 5.0LX

If it's sputtering and dieing when you shift, you probably have a bad lower shift cable that is holding your shift interrupt switch in the on position which kills your spark.

 

[waterone1@aol.com]

Re: Idle Problems - 93 Mercruiser Alpha 1 5.0LX

Don has a valid point if this problem occurs when you are actually shifting the outdrive. Just to be sure, if the boat is in neutral and you have the throttle raised to where it is idling, does it die as soon as you move the throttle back to the center position (without engaging or shifting gears) ? If it happens whithout any shifting it most likely is not the shift interupt.The shift interupt switch is located on the starboard exhaust elbow (where the shift cable from the control meets the lower shift cable to the outdrive)it is the small roller switch with two wires on it. You might have a helper watch this switch while you move your controls. It should stay in the center until you are shifting FROM either reverse or forward to neutral. It should not move at all if you have the control in the "throttle only" mode. If you verify that this switch is not activating, I would just adjust the idle screw on the carb for propper idle and see how she does. If it idles right, runs smooth and has not lost any top speed....you're done.

 

[kburke1]

Re: Idle Problems - 93 Mercruiser Alpha 1 5.0LX

To confirm, the engine will die if the throttle lever is in the neutral position (straight up). I can use the throttle without shifting gears and move the throttle lever forward just a little and it will idle perfectly. Dies when clicked back into straight up or neutral position (no gear shifting). Based on your response I will try to adjust idle screw on carb. Thanks for the help.