Mercury Black Max 150 Stator problems

[Gansett]

I have a 1988 Mercury 150 Black Max on my 22-2 Flat back, i love the engine!! Loads of power (a little bit of a gas hog) but the way it launches the boat up on a plain really helps in the salt river i live on. Anyway when i got the engine it had a really bad idle, i did some research and found out it was most likely the the low rpm windings on the stator. I purchased a OEM Stator from the local shop, rented the nice mercury flywheel removal tool and changed the stator, had the boat in the water the next day. The engine idled perfect, and seemed to have a much smoother throttle up. That was last summer, now towards the end of this summer it started doing the same crappy idle thing so i checked the ohm reading of the stator, and one side of the low rpm windings was an open circut. Is this a common Mercury problem? or was i just unlucky??? It's a $170 part and about an hours work, is there a part maybe a coil or something that could be killing the stator? Any experience with this anyone could share would help allot! Cheers, Joe

[fitz73222]

Hey Joe,

Mercury stators were surely an issue and you can't completely rule it out but try this. Get the engine running and unplug the main harness plug under the cowling and see if it runs better or differently; It wont hurt anything except your tach won't work and you will be unable to shut the engine off until you plug the harness back in. I just went through this on my starboard 115 Merc. The engine would run for an hour or two and when I would throttle back the engine would start to run like crap and shut off. I checked the entire ignition system and couldn't find an issue, but I was never able to check the system when it shut down out on the water. Turns out the keyswitch was the root cause, trying to fade into ground and shutting the motor down. I replaced both keyswitches on each engine and ran her trouble free for 4 hours without a hiccup. Panel mounted keyswitches get water in them from washdown, etc and eventually start this issue. Your keyswitch could be original so its time! Seems to be the year of the keyswitch also experienced on some other members rides; not limited to Mercs.

[Gansett]

Thanks!! Its only a three year old key switch, but i know it gets water it! I made up a little rubber flap the goes over it when th key is out, but allot of times i start the washdown with the key still in, and get half done before i remember to take it out.  I will try this as soon as we have a warm spell!! Joe

[fitz73222]

I think wet key switches on panel mounts cause a host of degrading electrical problems over time because of resistance. My flats boat had the same problem when I had the engine shutdown at high speed and I could hear the water sizziling inside the key switch and eventually take out a voltage regulator and got the stator wires discolored and hot. I relocated a new key switch to a vertical position on the console and never had a problem again. I made new key switch protectors from some coil to wire boots that fit over the keys and prevent water from entering the switch.