225 EFI Intermittent power loss

[NoSloProcraft]

Serial in signature.

First time out and I noticed boat was sluggish and lost about 10mph top speed. Power came back randomly when running WOT, felt a kick and all was good.
Just started troubleshooting with a timing light to see if I had spark to all cylinders after swapping spark plugs.
Seems the entire starboard side is intermittent.
Swapped the top port and starboard CDM’s, same result, no spark on starboard.
Checked and cleaned all grounds and added a 10ga redundant ground to the ECM plate, no improvement.
Swapped the ignition ecu with a spare as well and no luck.

Any ideas, bad stator?

[NoSloProcraft]

Update, did a stator resistance test. Five of six stator wires at around 1100 ohms, one just under 1000ohms.
I cleaned the bundle of grounds for the stator, tightened back down and got the same readings.

Started the engine and checked starboard side plug wires again with the timing light. Had strong spark on starboard bank. Checked the port side, all good.
10 seconds later the idle sound changed and I rechecked the starboard bank. No spark on all three starboards again. I can sometimes get a weak erratic flash out of the timing light on number 5.

Seems like at first start startboard side has spark for a few seconds and then drops out.

2ok - 1 no spark
4ok - 3 no spark
6ok - 5 intermittent spark

[JOE54]

you check stator when it warmed ????

[NoSloProcraft]

you check stator when it warmed ????

Yes, the motor was on the muffs but up to operating temp.

[EuropeanAM]

Look for any discoloring in the stator.

In addition to the redundant ground to the lower ECU, run ANOTHER 10ga Redundant ground from the battery ground cable bolt, up over the top of #1, and attach to the same bolt all of the STB side CDM's are grounding to. Occasionally ground-crimps in these harnesses begin to fail- installing BOTH of the redundant grounds usually eliminates that problem.

[NoSloProcraft]

Look for any discoloring in the stator.

In addition to the redundant ground to the lower ECU, run ANOTHER 10ga Redundant ground from the battery ground cable bolt, up over the top of #1, and attach to the same bolt all of the STB side CDM's are grounding to. Occasionally ground-crimps in these harnesses begin to fail- installing BOTH of the redundant grounds usually eliminates that problem.

Thanks for the help.


Finally found my flywheel puller and checked the stator. Windings look good, no discoloration, all wires look good etc. Flywheel magnets look good as well.
Added two 8ga redundant grounds from the (-)bat cable bolt to the lower ECU and stbd CDM bundle.
Removed each CDM and bench tested per Mercury test instructions...all checked out ok.
Replaced all spark plug wires for the heck of it because they were original.


Started and ran for a few minutes and had spark on all 6 cylinders. Started on Starboard cylinders, moved to port, spark was good. Moved back to starboard and lost spark on all three starboard.

[NoSloProcraft]

Forgot to mention, Ohm’d out the crank trigger and checked the gap. Trigger was within 900-1300 range. Gap was at .022” which is within spec at .040” (+-.020”). Opened the gap up a bit to .035” just to be closer to the middle of the tolerance range. Haven’t had a chance to run since this adjustment but I doubt it’s going to make a difference.

[EuropeanAM]

0T264057 is a .035" gap engine, using ONLY QL77CC Champion Spark Plugs. Tolerance is .002" (not .020").

If you are still having difficulties, you might want to disconnect the ECU's and make sure the connectors are clean/tight.

[NoSloProcraft]

0T264057 is a .035" gap engine, using ONLY QL77CC Champion Spark Plugs. Tolerance is .002" (not .020").

If you are still having difficulties, you might want to disconnect the ECU's and make sure the connectors are clean/tight.

Are you referring to the spark gap? Plugs are brand new and set to .035.
I was talking about the crank trigger gap, Manual says .040 +-.020?

The ECU connectors were checked and everything is clean and tight. I pulled all connectors including the cannon plug and everything looks clean and tight. I opened up the cannon pins a bit with a flat blade screwdriver also to make sure they were all tightZ

[EuropeanAM]

Ok... crank sensor gap makes more sense. Recommend that be at .050" for best results.

If all is as described, see if you can find someone with a similar engine that might let you try their ECU's for a run.

[NoSloProcraft]

Ok... crank sensor gap makes more sense. Recommend that be at .050" for best results.

If all is as described, see if you can find someone with a similar engine that might let you try their ECU's for a run.

Thanks, mentioned in my first post that I swapped back to my stock ECU’s with the same results. I currently have a 300PM IGN and 250XB fuel ecu. Swapped back to stock with same results. Any other ideas?

[JOE54]

a shorted stop diode in any one cdm will prevent at least 2 others from sparking (test with warmed cdms)

[NoSloProcraft]

a shorted stop diode in any one cdm will prevent at least 2 others from sparking (test with warmed cdms)

Thanks for the info, that must be what’s going on. When dead cold I have 6 cylinders firing, 30-60seconds later entire starboard side goes down. I’m replacing all CDMS, they don’t owe me anything after 20years of service.

[JOE54]

id use genuine MERC if iws you

[NoSloProcraft]

id use genuine MERC if iws you

Thanks, that’s the plan. Putting in an order with Don’s shop tonight.

[NoSloProcraft]

a shorted stop diode in any one cdm will prevent at least 2 others from sparking (test with warmed cdms)

Pulled all CDM’s and tested again per testing instructions using a multimeter diode test. All checked out ok, warmed all CDM’s in the oven at 200° for 30 minutes and retested. All still pass the diode test, but I’m thinking at least one of these is intermittent as they come and go when in use.

[EuropeanAM]

In some cases the only way you can catch it is to test them while still on the engine, just as soon as you lose spark.

Other option is to swap in a known-good CDM (one cylinder at a time) until the problem ceases. This method does have a drawback, as it "assumes" that only one CDM is failing.

[NoSloProcraft]

Thanks all that chimed in, looks like the root of my testing problem was a bad inductor lead on my timing light. Ordered a replacement lead set and all cylinders fire as they should. Found one bad CDM and swapped it out, all is well.

[JOE54]

a shorted stop diode in any one cdm will prevent at least 2 others from sparking (test with warmed cdms)

[NoSloProcraft]

Well the saga continued after this thread, the CDM was one of my issues.

Still seemed low on power so I decided to have the injectors calibrated. Four were flooding, one was slightly lean and needed to be replaced.
While inside the motor I inspected the reeds, Cylinder #3 had a few small windows in the reed pedals, these are 10yr old Boyesen XB reeds and all secondary reeds had multiple cracks. Replaced the reeds and assembled the intake. Replaced the squeeze bulb with new mercury unit just because I had one.

Took it out for a test and the motor stalled repeatedly off idle like it was running out of gas. Pulled the boat and I had a feeling the fuel hose liner bunched up when installing the new bulb.
Sure as sh*t when I pulled the bulb at the ramp it looked somebody stuffed a sandwich bag in the fuel line. The liner was separated completely and was actually collapsed in the 5/16" line from the bulb to the pulse pump, this is the newer blue line 5/16" Merc fuel line. The 3/8" line from tank to hull fitting was ok, but replaced it as well.
Fuel lines are maybe 8 years old, replaced when I bought the boat because it had the orange line Merc hose.

She now runs like a raped APE!