I?m hoping someone can give me some advice or suggest a course of action. I have a 1985 Mercury 18xd outboard. I have owned this motor from new and it has performed perfectly over the years. The motor has no more than 200 hours on it and has never required service other than plugs, fuel filter and lower unit lube ( maintenance I?ve done myself ). The motor is run dry of fuel and fogged every fall then basement kept.
This spring when I went to the lake the motor started on the first pull. The motor idled well and accelerated fine to about half throttle and then began to miss at high speed. When I returned home I got out my mercury service manual and when thru the normal checks. Fresh fuel, quicksilver oil mixed correctly, new plugs, checked fuel filter, all seemed well but still had high speed miss. Per the manual I checked the plug wires, coils, stator and trigger using a volt/ohm meter and all were within limits. I understand that the resistance measurements are not allows a good indication if the part is working properly or malfunctioning.
At home I setup the engine to run using a watermuffs, cleaned the plugs, and started the motor. Reading the plugs: Ran it at idle for two minutes and stopped the motor. Removed and inspected the plugs and all looked well. Reinstalled the plugs and ran the engine at half speed ( before the miss started ) Stopped the motor while running at half throttle and removed the plugs. All looked good. Reinstalled the plugs and ran the motor to full throttle ( motor is now missing ) Stopped motor while running at full throttle and removed plugs. The top cylinder was fine but the bottom cylinder plug was dark and fouled. Ahhhh. Was it the coils, switchbox, stator or trigger ?
Well, lets switch the coil leads from the switchbox and see what happens. Switching the leads from the switchbox causes the top plug and coil to foul.
The white/green wire and coils #1 has caused the plug to foul and then the white/green wire and coils #2 cause the plugs to foul. This eliminates the coils. The problem is in the switchbox, trigger or stator.
The resistance test for the trigger and stator were within limits. Does this mean the switchbox is bad ? The switchbox is a $125 item online and I do not want to throw away money if it could be something else. I understand there are no easy tests for the switchbox. The local merc dealer wants $100 to analyze the motor ( he says switchbox must on the motor for testing ) and if the switchbox is bad they want another $175 to replace it.
The switchbox looks like an easy replacement and I?d like to do it myself.
Any suggestions or advice would be greatly appreciated. Thanks??.
This spring when I went to the lake the motor started on the first pull. The motor idled well and accelerated fine to about half throttle and then began to miss at high speed. When I returned home I got out my mercury service manual and when thru the normal checks. Fresh fuel, quicksilver oil mixed correctly, new plugs, checked fuel filter, all seemed well but still had high speed miss. Per the manual I checked the plug wires, coils, stator and trigger using a volt/ohm meter and all were within limits. I understand that the resistance measurements are not allows a good indication if the part is working properly or malfunctioning.
At home I setup the engine to run using a watermuffs, cleaned the plugs, and started the motor. Reading the plugs: Ran it at idle for two minutes and stopped the motor. Removed and inspected the plugs and all looked well. Reinstalled the plugs and ran the engine at half speed ( before the miss started ) Stopped the motor while running at half throttle and removed the plugs. All looked good. Reinstalled the plugs and ran the motor to full throttle ( motor is now missing ) Stopped motor while running at full throttle and removed plugs. The top cylinder was fine but the bottom cylinder plug was dark and fouled. Ahhhh. Was it the coils, switchbox, stator or trigger ?
Well, lets switch the coil leads from the switchbox and see what happens. Switching the leads from the switchbox causes the top plug and coil to foul.
The white/green wire and coils #1 has caused the plug to foul and then the white/green wire and coils #2 cause the plugs to foul. This eliminates the coils. The problem is in the switchbox, trigger or stator.
The resistance test for the trigger and stator were within limits. Does this mean the switchbox is bad ? The switchbox is a $125 item online and I do not want to throw away money if it could be something else. I understand there are no easy tests for the switchbox. The local merc dealer wants $100 to analyze the motor ( he says switchbox must on the motor for testing ) and if the switchbox is bad they want another $175 to replace it.
The switchbox looks like an easy replacement and I?d like to do it myself.
Any suggestions or advice would be greatly appreciated. Thanks??.