Hello, yep 1st post but a longtime lurker. This motor has been running pretty well last season and this one until recently. Lately, when giving full throttle or even 3/4 from slow speed it has begun to bog heavily and will slowly increase power and RPM until finally getting up on plane and cruising speed. Earlier this season I went through it and replaced a lot of old fuel lines and rebuilt the fuel pump (OEM parts is all I use) and it ran great for awhile until this problem crept in.
I have the Mercury service manual and began going through the ignition diagnostic procedure after ordering a DVA from Electronic Specialties (1st unit they sent was bad and the 2nd one tests out OK). When trying to get a peak voltage reading on any coil my meter will not slow down and give anything that resembles a steady number. Not even close. ESI suggested that I test the DVA and digital meter (my own personal tried and true unit) by reading AC voltage from a house wall plug. So, I set the meter at 200VDC and using the DVA adapter I read the voltage and as per ESI got the correct reading of around 170VDC. I write all this to show that I've tried everything I can to test the voltage from the switch box to the coil and I just cannot get a steady reading. Period.
Moving on through the test procedure in the service manual I checked spark with a spark gap tester set at 10mm gap and found both strong and weak sparks on various cylinders on each bank. I get the strongest sparks on cylinders 1 and 2 but the cyls at the bottom of the banks have the weakest sparks with nothing else changing.
I am about to check the stator and trigger coils various resistances and will report back to this thread with my findings. Right now, I'm quite tempted to just order a new stator from CDI and switchboxes (2) but I'm going to hold off until I have confirmed a good reading on the trigger. I'll also take a voltage reading of what I'm getting off the voltage regulator.
1992 Mercury Black Max 135hp Serial number: 0D081129
Boat: 1992 Starcraft SFM190
Further testing:
Switchbox Bias Circuit Test reads -7.5VDC@1000RPM (normal as per SM)
Stator Low Speed Test is consistently above 300VDC@1000RPM (high)
Just on a hunch I checked the voltage at the battery while running 1000RPM and found 17 volts steady. According to the SM this is a "Constant High Output" condition. So, I'm off to pull the flywheel and visually inspect the stator and grab the part number off it if visible.
Any suggestions, tips or tricks are appreciated.
Thanks!
I have the Mercury service manual and began going through the ignition diagnostic procedure after ordering a DVA from Electronic Specialties (1st unit they sent was bad and the 2nd one tests out OK). When trying to get a peak voltage reading on any coil my meter will not slow down and give anything that resembles a steady number. Not even close. ESI suggested that I test the DVA and digital meter (my own personal tried and true unit) by reading AC voltage from a house wall plug. So, I set the meter at 200VDC and using the DVA adapter I read the voltage and as per ESI got the correct reading of around 170VDC. I write all this to show that I've tried everything I can to test the voltage from the switch box to the coil and I just cannot get a steady reading. Period.
Moving on through the test procedure in the service manual I checked spark with a spark gap tester set at 10mm gap and found both strong and weak sparks on various cylinders on each bank. I get the strongest sparks on cylinders 1 and 2 but the cyls at the bottom of the banks have the weakest sparks with nothing else changing.
I am about to check the stator and trigger coils various resistances and will report back to this thread with my findings. Right now, I'm quite tempted to just order a new stator from CDI and switchboxes (2) but I'm going to hold off until I have confirmed a good reading on the trigger. I'll also take a voltage reading of what I'm getting off the voltage regulator.
1992 Mercury Black Max 135hp Serial number: 0D081129
Boat: 1992 Starcraft SFM190
Further testing:
Switchbox Bias Circuit Test reads -7.5VDC@1000RPM (normal as per SM)
Stator Low Speed Test is consistently above 300VDC@1000RPM (high)
Just on a hunch I checked the voltage at the battery while running 1000RPM and found 17 volts steady. According to the SM this is a "Constant High Output" condition. So, I'm off to pull the flywheel and visually inspect the stator and grab the part number off it if visible.
Any suggestions, tips or tricks are appreciated.
Thanks!
