1988 Mariner 90 hp 3 cyl running issue

[Traceyh]

Ok, to start, I am a Honda technician in their motorcycle line, so I consider myself a fairly good mechanic.

Heres my problem

I have a 1988 90 hp Mariner 3 cylinder outboard.
I have gone through the fuel system, the carbs are clean, all jets and air passages are clear, float levels set, fuel pump working properly, primer bulb stays firm during running.

Ignition system, I have spark at all times, as indicated by an inductive timing light, and an inductive tachometer. I have replaced the spark plugs with new NGK plugs of the type that was already in it.

I just bought the boat, took it out for the first time. Pulled away from the dock, accelerated up to speed, was running fine, all of the sudden I dropped a cylinder, it began missing very badly on one cyclinder, and at times, another cylinder would drop out. I removed the spark plugs out on the water, and they looked ok, but as you already know, plugs can fool you. I didnt have any replacement with me at the time, so I limped it back to the trailer.
Got it home, put on the muffs, and engine is missing badly, but timing light and tach show spark on all cylinders.
When I removed the carbs, I also inspected the reed valves at that time, and all were intact and in good shape. I ran a compression test also, with 105 PSI on all cylinders, multiple test on each cylinder.
I already know I need to get a manual, which I plan on doing.
I have a DVA adapter on the way from CDI Electronincs, for testing the the trigger voltages from the stator, and from the "switch box" to the coils.
Now heres my thoughts so far.
I never "seem" to lose spark on any cylinder, however it continues to "miss".

Is the switch box giving a pulse to the coil at the wrong time?
Could it be bad fuel? ( I dont know how long the fuel has been in there, but it ran great for the first 3-5 minutes, then failed.)
What other problems could I be overlooking, as I havent done a lot of outboards?

Any help would be appreciated.

 

[Faztbullet]

Re: 1988 Mariner 90 hp 3 cyl running issue

Tank a fuel sample as it could be water...

 

[Texasmark]

Re: 1988 Mariner 90 hp 3 cyl running issue

I'll agree with faz. I'd dump the whole tank, put in fresh, using a wooden stick (slightly sharpened pop sickle stick works fine) depress the valve in the end of the fuel line at the engine connection and pump fresh fuel into the fuel line with the squeeze bulb. Reconnect the fuel line then drain the carb bowls and while the bowl drain screws are out, pump fresh fuel through the engine.

I have that engine ('02 version) and other than a stat problem the only problem I had was a CDI module failure. Interesting failure: When you first start up on the outing, the engine is cold and 1 cylinder is obviously inop. By the time you get the trailer put up and get out to the "no wake" buoys, the engine is usually warmed up somewhat.

Initial plane out attempt is rough till the lagging cylinder clears out all the accumulated fuel and away you go with no further problems the rest of the day's outing.

After some serious troubleshooting and thinking, I found that one of my CDI packs had a thermal problem when cold.....no spark, which corrected it'self once the engine warmed up. A new $100 pack and problem solved.

I had to jury rig a DVA to find it since I didn't have one at the time. Not sure that would have helped however as I had to catch the malfunction at the right time (temp) to see it.

My 2c,

Mark

 

[Traceyh]

Problem Solved

Problem Solved

Problem solved.
I received my DVA adapter from CDI, and proceeded to troubleshoot the ignition system, all DVA tests were within spec. So the last thing in the ignition system was of course the most overlooked thing on these engines... Spark Plug Wires.
I removed the wires from the coil packs, and they were covered in a wet green copper oxide that will pass spark to a timing light or inductive tact, but not sufficient power to spark a spark plug. I cleaned the insides on the coils, repaired the terminal ends of the wires and now she runs great.
Lesson learned.
Thanks for the replies.