225 Opti Max not firing on port side

[GMills]

I have a 225 Opti Max but the serial number sticker is gone and I haven't been able to find the number in another location. The boat is a 99 and I believe the motor is original. Numbers on the ECM are DFI ECM 99MY if that indicates it may be a 99.
I have analog instruments. Motor history is unknown and it has only been run on a water hose. This is my first post so forgive me if I overlook anything, I have read all the information on the site that I can before posting. Motor will start and idle but port cylinders are not firing and starboard side plugs are very rich appearing. What I have done so far is new DEKA 1050 MCA battery, checked fuel pressure, both electric pumps were bad, 90 psi steady when idling now, new plugs, new thermostats, and all injectors have been cleaned. I have cleaned every electrical connection, grounds, hot wires etc. Swapped coils from port to starboard with no difference. Checked spark on each coil with a spark tester though I only had the gap set at about 1/8". The middle coil on the port side will not fire even after swapping to another coil that was firing but as before all cylinders on port are dead. Verified by pulling plug wires while engine on idle. I have a set of test lights that can be used to see if I have a signal for the injectors to fire and the ones under the rail all make the light flash fairly bright but the ones on top of the rail give a very faint flash on the light, even the cylinders on the starboard side. I dont know how much voltage it sends to fire these so it may be normal? I have not been able to verify the air pressure but hopefully this weekend I can get something setup to do that. I might have given information overload but wanted to include all I could. If anyone can point me in the right direction to troubleshoot this thing I greatly appreciate it. Starting to question if it may be the ECM.

[JOE54]

izfr5g plugs ???? installed / so no flash of timing light connected to each plug wire ??????

[GMills]

I will have to verify the part number on the plugs. First time I checked I didn't get a flash from the timing light on port but did on starboard but I'm shy of my light. It's 30 years old and the second time I tried it I was having trouble getting a flash on the starboard side with it idling.

[GMills]

IZFR5G plugs. Checked for fire again with spark tester set at 3/8”. Still no fire on port side swapped coil from starboard again just to double-check still no fire. Checked ground wire for each coil back to the block and all grounds are good. Turned key on and checked for power to each coil but didn’t find power to any of them. The book says power to all six coils when key in run position and main relay pulled in. I’m a little confused why I don’t have power at least to the ones firing. Book also states negative terminal of the coil primary is connected to ground through ECM. Is there a way to test that other than ohm the wires. I don’t want to short anything out if it’s not already shot.

[lpugh]

red/yellow wire powers the coils and coil drivers, check for key on voltage to both bank with tester grounded to the motor block. It derives its power from fuse block and feeds all these circuits, the fuse is powered by a connection from the power point on the slave solenoid.
I do not have a specific diagram for a 99, but mercury is fairly consistent on how they do this, I believe yours is the same or very similar. Don or Joe be along to verify, I don't this circuit depends on the master relay.
If it does though you will have test with running or cranking as the relay will time out if it does not see a crank signal
After all that if you only have voltage to one bank of coils it has be wire harness issue, not very likely.

[kris_tx]

Could it be shift switch?

[JOE54]

shift switches should not effect spark they interrupt injector operation

[GMills]

I have power to every coil and ground to each coil. I attempted to test the ground signal from the ECM by attaching test light to 12V at the battery and test probe to the green wire on each coil hoping I would receive a ground signal from the ECM while cranking but no light flash from any coil so I assume it doesn’t work that way. I did ohm all the green wires back to the ECM and they were all good. I did notice the wires for cylinders 2, 4, and 6 which are not firing are all next to each other where they plug into the computer so leads me to think the computer might be bad.

[JOE54]

sure would help if we had ser number for this engine

[GMills]

If anyone can point me where to find it I would love to have it too.

[JOE54]

check on split line of block and for welch plug just below poppet cover

[lpugh]

the wire that the pcm grounds is a switched ground that operates coils. Only switches when a crank sensor signal is present. Due to what we call primary voltage feedback it may spike as high as 400 volts. Test may pop a bulb. Should ne checked with a DSO or lab scope. Scan tool has a coil test feature to drive this circuit for testing.

[EuropeanAM]

You might also need to break out the signal/ground circuit and perform circuit tests on that lead.

[GMills]

Stopped by my local Mercury mechanic that has a good reputation and he agreed it was probably the ECM. He had a good used one and offered for me to bring the boat by and try it there and if it was the problem he would sell me the used ECM. Took him up on it and that seemed to be the problem so I bought it. Just ran it on muffs and all cylinders are firing on the timing light. I’ve never owned an opti but seems to have a little hiccup occasionally idling. I’m going to water test when I can and see what happens. Thanks for all the help and I found the serial on the plug next to the poppet. 0G870915.

[JOE54]

PCM come from same hp and same igni system engine as yours , lucky man

[JOE54]

born on 11/6/98