2004 F115 not firing on cylinders 1 and 2

[Navy SeniorChief]

Please help. I have a 2004 F115 that seems to be not firing on cylinders 1 and 2 (no spark). I took the boat out about 2 weeks a go and noticed on the way out that the motor seemed a little sluggish. Through out the day the motor seemed to get worst. I thought maybe the Fuel/water sep was dirty so I changed it and the engine-mounted filter also. Still not working. Motor still missing.

Took it to the marina today to do some troubleshooting. I can start the motor up. It will idle, but shakes. I pulled the plugs out (all 4, one at a time and noticed that plug's 1 and 2 were wet with fuel, but plugs 3 and 4 are dry. Figured I would change the plugs and things would be good to go, but no luck. It still appears that cylinders 1 and 2 are not firing. I can pull plugs 1 and 2 's spark plug wires off while the motor is running and there is no decrease in RPM's. If I do that the plugs 3 or 4 the motor dies.

The ignition coils work like this, the top coil goes to plugs 1 and 4, and the bottom coil goes to plugs 2 and 3. What are the odds of both coils going bad at the same time?

Please help.

[99yam40]

Have you checked to see if you are getting spark on all of the plugs?
If the coils feed 2 plugs and the others ones on that coil work then I would bet that if you used a spark board it would show they are all sparking and you have a fuel problem unless the wires are bad

[Navy SeniorChief]

99Yam40, Thanks for the reply, I havn't checked to verify the spark on cylinders 3 and 4 other than just visually looking at them. What is a spark board ?? Can I get one from the local auto shop ??

[99yam40]

spark boards are just something to hook the plug wires onto with a ground to the motor to be able to see the spark on all cylinders and how far they will jump or at least that they jump the required gap distance for proper firing

from what I understand about the 4 cylinders with 2 coils, they fire 2 plugs at a time, one is a waist spark as it is not needed and is on the exhaust stroke and the other is on the power stroke. So if one off of the coil is sparking the other should be also.
You need compression, fuel, and spark at the right time to run properly. If your compression and spark at correct then it would have to be the fuel mix.
Compression and spark are the easy ones to check then go to fuel.

[Navy SeniorChief]

I have read a few things about the VST being clogged. When I brought the boat home the other week, I checked in motor filter (small waffer type on the back of the engine) and it had black particals in it. I'm assuming the black particals were peices of the fuel hose breaking down. I wonder if some of that made it way to the VST and it's clogged ??

[99yam40]

I am not an expert on these motors, but I am just giving my opinion in general about the workings of some of the systems and I could be wrong. So take it as you may.
From what I have read VST and injectors screens will clog and need to be looked at from time to time. If your compression is good and you have good spark I would be looking at fuel before you hurt the motor from running too lean.

[Navy SeniorChief]

What do you mean trigger ??