Don,
I have a 2006 Mercury Verado 275 HP serial #1B301246.
Back in 2012 the dealer replaced all 6 of the pencil coils. Mercury relations picked up the tab for 2 of the 6 and I paid for the other 4. Since then I have only put 49 hours on the motor.
The first time I took it out this year, I could not get it on plane. The RPM's would go up to around 3500 the motor would shudder and RPM's drop to around 3000. Tried multiple times and the same thing kept happening. Similar to the symptoms I had back in 2012.
Took it in for service. The Verado Certified mechanic hooked up the computer and tested each pencil coil but all showed good. He was not able to test under load as if it were on the boat. When he pulled the coil from the bottom plug he noticed some moisture when he tapped it on his hand. He could not determine where the water had come from.
I purchased a new pencil coil and put it in the bottom plug where the technician found the water. First time out I was on plane in about 3 seconds without any hesitation. Started and stopped about a dozen times and it ran just the way it should. Looks like the coil failed under load.
The question I have: is there any way to test the coil to determine if it is good or bad other than under load?
Thanks in advance for the help
John