89 140's plugs foul

I have twin 140's that I cannot get over 4800 RPM's on them currently. I have had them up to 5500 RPM's in the past and had alot of power. They now sound like they are overloaded and just dont have any balls. I have replaced the spark plugs (ql77jc4) 3 times over the last couple months and the motor would run fine for a week or so. I have just purchased NGK bpz8hs-10 plugs that have a higher heat range to hopefully try to fix my problem. Will these plugs damage my outboard? I have been through everthing on these motors and I'm going bald fast! I know most do not reccommend NGK for OMC but I was hoping it is worth a shot.

Verify spark on each cylinder. I believe it should be able to jump a 7/16" gap.

Verify you have good compression in each hole.

Look through each carb throat with the engine running to see if any fuel mist is being sprayed back out. If it is, you could have a bad reed(s).

Quite possibly you have a bad float or needle/seat that is allowing too much fuel to flow into then engine. You might as well pull the carbs and clean and rebuild them all. be sure to install new floats and needles in each bowl.

KJ

Odd that BOTH engines would display the same symptoms unless you have a fuel related problem. Check the fuel connections from the tank back to make sure you don't have any leaks (sucking air). When you say the plugs "foul" what do they look like?

Plugs are dark and wet. One motor used to run better (port) than the other till the last time out. I have rebuilt the carbs (new needle and seats) on both motors and have replaced the fuel lines all the way to the tank. I have pulled a vacuum on the lines from the engine to the tank and they are fine. Reeds are fine. I just checked the spark and it jumped 7/16 on all cylinders. I also checked to see if the plugs sparked, grounded them and they all did (i guess there not fouled). my fuel is fine, I ran off a 5 gal tank to be sure. The compression is (stbd) 125, 125, 112, 125 (port) 121, 121, 121, 121. Found a loose wire on the port motor so that could explain why the last time out it would not rev up to 5500 rpms. Could the low compression on one cyl make the stbd motor not rev past 4800?

Remove Black/Yellow wire that leads FROM engine wiring harness TO powerpack (both engines).

Using a ammeter of volt meter set to lowest setting, attach meter wires between the wiring harness Black/Yellow wire and a powerhead ground.

Turn key to the ON position (engine NOT RUNNING).

If any voltage at all registers, even a microvolt, the ignition switch is usually suspect, in which case replace it.

To test the ignition switch, remove the Black/Yellow wire from it. If voltage registers with it connected to switch but does not when it is disconnected, then obviously the switch is faulty.

Any battery voltage applied to that Black/Yellow wire will affect and eventually destroy the powerpack(s).

If there is no voltage problem as mentioned above, visually inspect the stator(s) under the flywheel(s) for cracks and a possible sticky looking substance dripping out of them down upon the powerhead(s). That dripping would indicate that the stator has overheated and is failing which results in weak, erratic, and eventually no ignition. Should this problem exist, replace the stator.

Joe,

Loose wire was the problem on the port motor. Fixed and rpms go to 5500 now.

I finally had a chance to do the test power pack kill circuit voltage test. The port engine had .8v and stbd had .2v when the key switch was turned on and 0 when the switch was off. There was no voltage when the wires were disconnected from the key switch. I was doing some research on CDI Electronics site and it says its ok as long as it is below 2v. Is this wrong? The port engine has a brand new key switch and it is reads .8v out of the box.

I pulled the flywheel's and removed and inspected the stator's. No melted sticky stuff on the stator. The stator test results were ohm-420 & 150v which I believe are within spec.

I also checked the DV cranking output of the power packs and they were between 80v and 120v. The book calls out 150v+, are my packs going bad? I still have good spark.

I also thought about rigging up a grounding switch to ground the spark plugs cyl by cyl to find the problem cylinder while running at wot. Is this a bad idea? will this hurt the electronics on the motor?

I'm not about to get into an argument with CDI about electronics BUT.......

On the back of the ignition switch, there are two (2) "M" (magneto) terminals. One terminal has a black wire attached to it that leads directly to ground. The other "M" terminal is the one that has the black/yellow wire (pack kill circuit) attached to it.

When the key is in the OFF position, there is full continuity between the two "M" terminal which effectively shorts out the powerpack and kills the ignition.

When the key is in the ON position, there is absolutely no continuity between those two "M" terminals...... the "M" terminal that has the black/yellow wire attached is now connected to absolutely nothing........ assuming that you did disconnect that black/yellow wire from the powerpack, so this creates somewhat of a mystery as to where that voltage is coming from.

Possibly you have other wires connected to that black/yellow wire "M" terminal? If so, remove them..... there must be no other circuits connected at that point.

It's been my experience, and that of many other mechanics that any voltage applied to that black/yellow wire = powerpack failure.

I don't have the books on the 1989 140 model so I can't verify the readings BUT hopefully someone with that knowledge will jump in here with those numbers.

On those engines, watch out for the thermostat system and engine temps.
Be sure engine reaches correct operating temp on BOTH banks.
If impeller more than 5 yrs old, change!
Give a good run of Engine Tuner/Sea Foam to clean out carbon deposits.
I would have stayed with the Champion plugs.

Joe,
Yes I disconnected the wire at the powerpack and tested the wire coming from the key switch. I will disconnect from the key switch and see if it originates from the m terminal. There are no other wire's connected to the black/yellow wire at the switch. I have the oem manual for the engine and it does not say anything about testing this circuit for voltage. I will look into purchasing a new dual switch assembly.

Haffiman
I had problems with the thermostats and replaced them. I have a infared temp sensor and they are reaching normal operating temperatures(145) when measured at the thermostat pocket. Changed Impeller last year. Used evinrude tuner and decarb 2 months ago. I have decided not to go with NGK and have stayed with champion.

I dont think my problem is fouling plugs but something different. My port motor is running great now (sounds strong, has alot of power and will rev to 5500 rpm at wot) my stbd motor will only rev to 5000 and sounds like it is struggling. I think it is not running on all 4 cyl's. I am getting good spark on all cyl's. I'm going to go through the link and sync one more time to see if it helps. If not I'm going to rig a switch to ground the spark plugs one at a time while I running at wot the find the offending cylinder. All of the following has been done/replaced to each motor:

Fuel Lines, Fuel Filters, Carb Rebuild, Spark plugs, Spark plug wires, Thermostat, Water pump, link & Sync, De-carb, Vro Removed, primer ball, Timing.

No, the voltage thing...... You won't find that in the manual. It's one of those things one learns thru the years.

(If impeller more than 5 yrs old, change!)---5 years......old..........even if u inst one today...........never run it,......it should be repl no ltr than 2.....my opinion....nope......

its simply,..rubber vanes....that take a set......