1997 Mercury 60 hp 2 stroke fouling plugs

[100TonCaptain]

Hello, I have the above stated motor that I bought recently. It has a rebuilt powerhead, but I am having problems with the motor fouling plugs out. It cranks and runs fine, but in mid range it wants to hesitate, and pop. I did discover some electrical tape on the #2 plug wire .. Would that one cylinder not getting good fire cause all 3 cylinders to foul the plugs? Or am I looking at a 2psi check valve problem? I thought I would include that I transported the motor home laying on its side, and it stayed that way for about a day and a half before I could get it upright to install using a chain fall. The oil tank was full while it was laying on its side. The plug wire on the #2 with electrical tape looks otherwise fine. What would cause the plugs to foul almost instantly with liquid oil on them?

 

[James R]

Rebuilt power head is possible but were the carbs cleaned and rebuilt correctly. Is it the original power head. If so what caused the failure. Change that plug wire. The bad plug wire casts doubt on the rebuild.

 

[Texasmark]

Got to walk through everything to see if it's in spec. Is the oil there because of excessive oil from the oil pump (assuming it/s still VRO equipped), or is it caused by lack of proper ignition spark, or bad timing, or as James said, are the carbs set up properly including the settings of the low speed jets.

 

[100TonCaptain]

I have since removed the oil injection from the motor, replaced plug wire, and it still fouls plugs. Once I clean them very good, reinsert them, and run it, it runs great for half a min then surges and hesitates and pops. In the water, mid speed before achieving plane, the boat cuts in and out providing glimpes of what it should be, only to slip back into sluggishness. Every once in a while , around 2500, while its surging and bucking, the motor will break through and run like it should for a short time. But mostly I run it passed that rpm to the dash, and it gets on plane, but not like it should. I am thinking it could be a stator issue. As far as the carbs, I feel they are fine. The motor runs fine with new plugs for a short while. But then fouls quickly. It idles like a champ, and low speed is good. Anything in mid range on muffs and in the water it will pop , and hesitate. I can run it for 2 mins with fresh plugs, and take them out and they are oily.

 

[Texasmark]

I too think it's a stator. If I understand the trigger circuitry, you have one pickup coil adjacent to the inside of the flywheel, but 3 magnets in the flywheel 120 degrees apart. Each time one of the magnets in the flywheel passes the pickup coil you get a pulse. The pulses are routed to the CDI circuits in series so that each gets a chance to fire when a pulse comes down the line.

Since only one cylinder is ready to fire at any given time, even though all 3 plugs fire, only one results in an explosion and power stroke. With that said, a problem under the flywheel will affect all triggers and combustion in all cylinders.. Could have a bad connection somewhere along the path of the triggers from the source through the 3 circuits or the pickup coil may have an intermittent connection. Might swap the CDI's around to see if anything changes....like if the first to receive the triggers is bad (whatever that is) it may keep the others from getting their shot at it. If you put the bad one (if that is what it is) at the end of the string by swapping them around, it might allow 2 cylinders to fire consistently and expose your smoking gun. Otherwise pop the flywheel and have a look at the trigger pickup coil and see that the magnets are intact.

You also have probably 6 pickup coils for your battery charging alternator as I recall and the yellow wires (on mine) are your exit leads for those. The trigger coil is different from them.

 

[DavidMoore]

The fuel is not being burned properly, there's either too much of it or it's not being ignited in the way it should

In addition to what's been said, I would be double checking that choke system is actually functioning normally (i.e not staying on), the correct plugs and heat range are being used, the quality of spark (should jump 7/16"), ignition timing at idle and WOT, carbs settings and that they are not flooding due to bad floats / leaking inlet needles.

 

[100TonCaptain]

I want to thank you all for responding. Is it a tough job to replace a stator? This motor is a replacement for my 1984 3cyl. Mercury 60hp, and the stator was good on it. I'm pretty sure it's the same stator for this motor. Anyone know for sure?

 

[Texasmark]

Over the years Merc upgraded their trigger circuits whereas in the later years (2002 for a number) you had 3 Capacitor Discharge Ignition modules and the stator. Everything was in the CDIs except the stator and the spark plugs. In earlier models you had a box full of "stuff" with all the wires going and coming from that box...switch box they called it, but it did the same thing and probably used exactly the same signal pulses. Since you are talking about triggers, signal circuits, you are talking about low voltage signals with high impedances (low voltages and low currents) which translates to probably won't hurt to try. Not like you messing with the other end with high voltages, or high currents that can burn holes in circuits.

If it looked doable, I'd chance it if it were mine!