30 hp Johnson kills at idle speed

[JerryMac]

I have a 1993 30 hp electric start Johnson running on a 16.5 foot Grumman aluminum bass boat. The motor seems to start easily when cold and with the idle control on high will run normally for 30 sec or so and then starts to lose speed and stop. If when this happens (the loss of speed) I press on the choke 2 to 3 times (the choke is built into the starter key)it revs right back up and runs normally again for several seconds. I can repeat that process several times. However, if I leave it to idle or try to run it at trolling speeds (about 1100 rpm) it will kill. If I run it at high speeds (3500 to 5000 rpm) it will run until I run out of gas. The compression is good. The plugs seem to be fine. The gas is last years. I don't know much at all about carberators. What you can see externally looks clean. I think I know what screw is the idle speed adjustment. Any suggestions would be appreciated. Thanks.

 

[JB]

Re: 30 hp Johnson kills at idle speed

Hi, JerryMac.<br /><br />First, be sure that you don't try to adjust the idle with no load on the engine.<br /><br />Then get yourself a Repair Manual. It will be the best $30 or so you will ever spend on that engine.<br /><br />Good aftermarket manuals here: http://www.boatmotors.com/manuals.html <br /><br />Or OEM Manuals here: www.kencook.com.<br /><br />Sounds to me like she needs at least a "link 'n' synch" adjustment procedure or at worst a good carb overhaul. A snap with the manual.<br /><br />Good luck.

 

[G DANE]

Re: 30 hp Johnson kills at idle speed

If is was left with the gas from last year in it, i recommend you clean the carb first, dissasemble it, remove all plastic and rubber parts, soak it overnight in carbcleaning solvent, blow thru all passsages, especially iddle and intermediate circuit with compressed air, assemble everything again. Then adjust sync´n linck, iddle mixture and speed. Be sure not to tighten low speed needle too much against seat when you do the initial set at 1 3/4" turns from bottum. You will need a manual for this.

 

[JerryMac]

Re: 30 hp Johnson kills at idle speed

Thank you both for your replies and advice. I will order a manual and get after cleaning the carb. Assume the manual will describe the "sink and link" Thanks.