jackspivey2
Contributing Member
"Really more annoying than any
"Really more annoying than anything, but I would like to hear any input as to the cause of this quirck. 93 5.8 EFI Omc. When I start it up to back off the trailer, the tach will sweep up to about 3000 rpms then slowly fall back to reading normal. Motor is running about 900 rpms the whole time. Then as I back out and let it idle or just above idle the tach will jump around a bit as the motor warms up. If I apply the throttle to get up on plane sometimes the tach will go all the way up to 6000 rmps, however I know the motor is only running in the 3000 rpm range. After a bit of running it calms down and starts reading accurate and the fluctuations will stop after about 15 minutes of boating. It's not a detrimental problem, but as I am selling the boat to a friend who has never owned a boat and knows nothing about them, I would like to fix it and give him a better chance at having a positive boating experience!! I guess my question is more toward this.... Is the tach still driven from the coil on an efi motor or is this something the coming from the "brain box"? I suspect a possible bad spark plug or something backfeeding the coil untill the motor gets up to temp and the plug starts firing again.. ? Any help is greatly appreciated!!
Jack"
"Really more annoying than anything, but I would like to hear any input as to the cause of this quirck. 93 5.8 EFI Omc. When I start it up to back off the trailer, the tach will sweep up to about 3000 rpms then slowly fall back to reading normal. Motor is running about 900 rpms the whole time. Then as I back out and let it idle or just above idle the tach will jump around a bit as the motor warms up. If I apply the throttle to get up on plane sometimes the tach will go all the way up to 6000 rmps, however I know the motor is only running in the 3000 rpm range. After a bit of running it calms down and starts reading accurate and the fluctuations will stop after about 15 minutes of boating. It's not a detrimental problem, but as I am selling the boat to a friend who has never owned a boat and knows nothing about them, I would like to fix it and give him a better chance at having a positive boating experience!! I guess my question is more toward this.... Is the tach still driven from the coil on an efi motor or is this something the coming from the "brain box"? I suspect a possible bad spark plug or something backfeeding the coil untill the motor gets up to temp and the plug starts firing again.. ? Any help is greatly appreciated!!
Jack"