Home page 

Outboardparts.com: your source for Outboard Motor Parts!

To Return


Tricks to Testing with Minimal Test Equipment

  ********      This information is supplied as a service guide only and Outboardparts.com is not liable for any misunderstandings, errors or omissions regarding this information. The information has been obtained from actual Unit analysis, parts manuals, and other sources.      ********

all Engines

Intermittent Firing: This problem can be very hard to isolate. A good inductive tachometer (fluke 88 is recommended) can be used to compare RPM on all cylinders up through wide open throttle. A big difference on one or two cylinders indicates a problem.

Two or more cylinders misfiring: It is recommended that both power packs be replaced, unless the problem is a bad Trigger.

Engine continuously blows power packs: When an engine starts blowing power packs repeatedly, especially on the same cylinders, replace the Ignition coils on those cylinders. The inductive kickback from a bad coil can destroy the packs, even if the coils check good with all known tests. A Stator that test good can also be sending spike voltages to the packs causing them to fail repeatedly.  

Visually check the Stator, Trigger and flywheel: Cracks, burned marks and bubbling on the Stator or Trigger indicate a severe problem. If the Stator shows bubbling around the battery charge windings, more than likely you will have to replace the rectifier/regulator in addition to the Stator. Signs of rubbing on the flywheel usually indicate a bad upper or lower Bearing. Check both the outer Trigger magnets for signs of cracking and to be sure that they are not loose.


Open type timer bases: When all cylinders fire with the spark plugs out, but one or more cylinders quit when the spark plugs are reinstalled, regapping the timer base may solve this problem.  Please refer to the Troubleshooting guide for OMC power packs and CD's item #8.
Quick Start timer bases:  These timer bases cannot be checked like the other timer bases. Please refer to the Troubleshooting guide for OMC power packs and CD,s item #5.
Engines with SLOW features: If the complaint is that the engine will not slow down after a few minutes and starts shaking real bad, (but the engine is NOT overheated) try replacing the temperature switch (the one with the white/black and tan wires coming out). Check routing of tan wires. Relocate as far from the spark plug wires as possible. Check blocking diode in engine Harness.

Mercury Outboard 6 Cylinder with ADI Ignition

No fire on the 1,3,5 or 2,4,6: Swap red and red/white wires, also blue with blue/white wires. If the problem moves to the other set of cylinders, the Stator is at fault. Disconnect rectifier and retest. If the engine fires normally, replace the rectifier. If no change, we recommend replacement of the Stator. If you replace the Stator and the problem remains try another flywheel, if possible.
No fire on one cylinder: Since this condition can be caused by the opposite switch box (pack), disconnect the white/black jumper between the packs and retest. If the dead cylinder starts firing, replace the pack that was firing all three cylinders. As a verification, swap the Trigger and spark plug Wire to the cylinder closest to the dead cylinder, (i.e., if #1 is dead, swap the brown Trigger Wire with the white one). If the problem moves to #3, replace the opposite power pack (switch box). If #1 is still dead, swap the green and green/white coil wires. If the problem moves to #3, replace the power pack (switch box). Please remember to put the Trigger wires in the correct order after you finish.
Always check the bias circuit: Disconnect the jumper between the packs on the white/black posts. Check the resistance from the white/black posts on each pack to engine ground. Standard packs will read from 13-15,000 ohms. Racing boxes will read approximately 9,600 ohms. MAKE SURE THAT the BIAS Reading is the Same on BOTH Packs!!! If the bias is out of specification on one pack you must replace both packs to prevent future damage. This circuit effects Ignition timing and could cause a powerhead failure. 
for more detailed information, please refer to the Troubleshooting guides on the other pages.

Go Back