CDI problem or not?

[oneqkbenz]

I have a 1992 150 two stroke. Great motor. I keep this boat in florida, so it is tough to keep maintenanced. A couple of months ago I got water in the fuel and had to drain the tank. I removed and cleaned all 3 carbs. When I tried it out, it ran great. I headed offshore, but only got about 3 miles when it sounded like I lost a cylinder. the motor ran like it was a 90. After fishing for the day, I came in and checked it out. #5 cylinder had no power. The plug fired, and when my buddy pulled the plug wire while the motor was running, the rpms never changed, but it shocked him through the pliers. All the other plugs dropped the rpms when they were pulled. I pulled the plugs and checked the compression. All cylinders fine. I then pulled the bottom carb thinking I had a stoppage in the float bowl. Everything was clean. I swapped ignition coils, no change. I changed out plugs, no change. The plugs were always moist, but never fouled, and when pulled, always fired. I had fuel, compression, and fire, but no power. I washed the boat, flushed the engine, and while it was running, I pulled the wire from the CDI to #5. No change. I then pulled the wire from #3. The rpm dropped. I plugged #5 back in and the rpms picked up! I then plugged in #3 and the engine rpms increased, smoothed out for abut 3 seconds, and then dropped again. I had to cover the boat and fly back, so I have not been able to diagnose any more. I hate to spend my vacation time working on the boat any more than I have to. I would rather be fishing. I will be going back for Xmas, and I would appreciate any suggestions on exactly what this problem could be.
Thanks.

[bumperfood]

"The plug fired, and when my buddy pulled the plug wire while the motor was running, the rpms never changed, but it shocked him through the pliers."

Spark is good, as your friend can attest to.

I think you have a fuel problem, and I think it's in the 5-6 carburetor. When you get back down to Florida, I would suggest you run the engine with the silencer removed, and squirt mixed fuel into the appropriate venturi. If the engine smooths out, the problem is either in fuel delivery or in the carburetor itself. If you cannot run the engine with the silencer removed (carbs are loose), you need to find another way to introduce fuel to the carburetor. One way would be to drill a hole in the silencer directly in line with the carburetor bore (don't do this with the silencer installed and make certain there is no drilling residue left behind) You can seal the hole when you are finished with the appropriate sized rubber plug.

[oneqkbenz]

Thanks for the reply. The motor runs excellent with or without the silencer. While I had the silencer off, I checked the timing, it was dead on. I also aimed the timing light into the carbs to watch the fuel atomizing, and I could see fuel spraying into #5. Like I mentioned, the plug never fouled, and was never dry. I could swap it with any of the other ones with no change. No matter how many times I pulled the plug wire, there was no change, except for the time I pulled the CDI wires. I'm going to spray some carb cleaner down the #5 venturi when I go back and see if there is a difference. That is the only thing I know that I didn't do.

I have never had any experiance with the CDI, and didn't know what the symptoms were when one startsto go bad.
I can usually diagnose engine problems using process of elimination, but this has me baffled.

[99yam40]

Testing with a peak reading voltmeter made for these ignition systems or using a DVA adapter to make sure the inputs and the outputs are in spec are the best thing to do in my opinion.
A Yamaha service manual will help if you are working on this motor yourself

[jb123]

run it on an aux tank ball and hose hooked to motor filter
prob need to reclean carbs
check low pressure lift pumps
where in fla ?

[oneqkbenz]

The boat is in Stuart. All the fuel is fresh, I had the tank pumped, new fuel filter installed, and rebuilt the carbs right before this happened. I had water in the fuel tank, and I went through the whole system. I can see the fuel spraying into the venturi. I just don't have any power.

[oneqkbenz]

I may end up taking it to the shop for them to analyze, but I was hoping to diagnose it myself and use the diagnosis money to put toward whatever part was required. I do have a Yamaha service manuel for this motor, but I have no experiance with a CDI, and do not know how and if they went bad. I usually don't have much time to take my boat to the shop in Florida, as I go on weekends and Holidays. It isn't much fun working on my boat during my vacation time, but I have to get it fixed.

[jb123]

check compression
check fuel pumps
clean/rebuild carbs
ohm caps
change plugs
you have spark, just a wet cyl so you dont hear the rpm drop

[bumperfood]

Just a thought. You may be shorting to ground at the plug wire, not likely, but possible. You can often tell by running it at night (in the dark) with the cowl off. You might see a spark around the outside of the plug.

[oneqkbenz]

Thought of that. When I switched the coil, I switched the wire also.
This thing has me baffled.

[Wellcraft238]

Outcome?

Was there an outcome on this? I'm chasing a potential CDI problem on mine now. I'm by Stuart as well...