Johnson 100 HP /100 ESL 72

[Offshoreboat]

HI,<br />During my vacation in croatia i had following problems with my 100 Johnson hydro electric shift engine,after cold start I can shift one time in reverse and after that one time I here the gears crunching but i have no reverse annymore.<br />second problem is that the engine runs GREAT for 4/5 minutes and after warming up it starts to misfires,it only goes worse as I run longer time.<br />I run on 95 octane unleaded fuel and Champion L78V plugs.Oil in my gearbox is the correct OMC type C lube.please any advise is welcome.<br />I think for the misfiring that my HT coil is playing up after it warms up but for the gear shift problems I DONT NOW!<br />thanks for any reply or advise<br />Offshoreboat

 

[Joe Reeves]

Re: Johnson 100 HP /100 ESL 72

Offshoreboat.... Check the wires that lead to the lower unit at the engine. Leave them connected.<br /><br />DO NOT have the engine running when doing this test.<br /><br />Attach a voltmeter (red) lead to each lead (both blue and green) one at a time, with the ignition switch "on" and the control lever in reverse. The black lead of the voltmeter is to be connected to a powerhead ground of course.<br /><br />You should get a reading of 12 volts at both wires. If you do not, it is usually due to a failing shift switch which is causing a voltage drop. The second cause could be frayed, faulty wiring (but it's usually the switch). This is assuming that your battery is in good condition and is at least a 70amp hour battery. A full 12 volts is needed at both of those wires, when in reverse, in order to obtain reverse gear.<br /><br />Your engine will accept a 87 octane fuel and it will cause no problems. And those L78V surface gap s/plugs really have no heat range to speak of even though they are rated "78". The engine usually runs better on Champion L77JC4 s/plugs, gapped at .030. You might want to give them a try.

 

[Offshoreboat]

Re: Johnson 100 HP /100 ESL 72

THANKS JOE CHANGED PLUGS BUT PROBLEM STILL THE SAME.COULD IT BE THE COIL WHO IS PLAYING UP?<br />ROLAND.