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Mercury Blackmax Ignition replacement

Adambomb

Adambomb

Member
A few seasons ago I had a Mercury mechanic replace my stator after having ignition issues. My motor is a 1987 Mercury 135 blackmax. The motor would only be firing 4 cylinders until about 10 min of running, after that the other two cylinders would kick in and the motor would run fine all day, I could shut it off for hours and it would still fire all six. but if it sat over night it was back to the same problem. After replacing the stator, the problem went away. But the issue has returned and after running it with the more annoying than troublesome issue, it's starting to get worse, the last two runs felt more like 3 cylinders before the others kicked in. :brickwall:
After reading some forums on the topic and hearing from some mechanics, I've decided to just go ahead and replace the coils and switch boxes. Does anyone know a good supplier of these parts? I'm leaning towards aftermarket, probably Mallory Marine after doing some research, they sound like a good option. One forum noted that they were higher quality than OEM and are cheaper. Does anyone have an opinion on this? Any help would be greatly appreciated
 
i dont have an opinion on the mallory parts but i did have the same type of problem on my 200 blackmax. i tested the switch boxes and replaced, had already done the stator as you have. switch boxes solved my issues. you will need a DVM to test it.
 
I did the same thing to my Black Max 200 last year. I found the cheapest place to get my coils and boxes was wholesalemarine.com I bought Sierra brand. Way cheaper than mallory or quicksilver and worked just as good!! My motor was acting exactly like yours and I was told that 9 times out of 10 when the stator goes out, it takes one or both of the boxes with it. The Sierra boxes worked great and the boat ran perfect after replacing.
 
Thanks fellas! I knew I'd get the info I needed on the forum. I guess I'll start with a set of Sierra switch boxes and see where that gets me.
 
You can also do an ohm test on you stator, its a pretty eazy test. all you need is a mutimeter, you can test both the high and low speed windings and see if you are shorting out. Get a manual and look under the diagnosic section for instructions. You just have to disconnect a couple of leads from the swich boxes and test across them with the meter. the mainteniace manual will have the ohm ranges in there, its better than spending a few hundred that you dont need to spend and you wil have more knowledge of whats going on with the motor.
 
So I ended up installing a new set of sierra switch boxes. I started the motor on the ear muffs to test them, and it ran great, all 6 cylinders. The next day I took it out on the water, it started right up and ran great for about 15 minutes, then all of the sudden it started running real bad. the motor would still idle ok, but would sputter when I gave it gas. I was so baffled that I took it straight to the marina and dropped it off. It seemed to me the switch boxes would have something to do with it since I just replaced them, but the issue is entirely different, my other concern is that I used ethenol fuel the last two or three fill ups, I usually use non-ethenol but was told by a merc mechanic it's ok to use as long as it doesn't sit in the system for too long without running it...I'm stumped
 
Could be some residual water in the system. Could be the trigger, stator, regulator, coils, wires, or stator. Keep us posted on the outcome. Just did some trouble shooting on a boat that had a lot of salt water residue buildup on the safety lanyard switch. The high voltage from the ignition system was tracking across the residue buildup and shutting off the ignition when the engine warmed up.
 
I had a stator issue a while ago, It would run great cold and as soon as it would warm up it would short out the high speed windings and shut down three cylinders. It would test OK but not once it warmed up. So it would idle fine, over 1000 rpm it would run llke crap. Good luck, hopefully its an ez fix for you.
 
One thing I have learned in the last few years is do not replace a mercury stator with a mercury or sierra stator. I went through two in two years with my boat. On the third try I installed a CDI stator and it has been flawless for the last 4 years.

I agree you first issue only running on a few cylinders until it got hot was indeed the switch boxes as mine did the exact same thing.

Also after talking to a few merc mechanics they said coils almost never go bad and they are easy to check with simple ohm tests.
 
Thanks for all the useful information everyone. I think by the time this engine trouble is sorted out I'll be an official on 80's vintage blackmax motors. An update on the motor, I got a call from the marina that my boat was done yesterday. When I picked it up I was Informed that for $215, the mechanic had replaced my 3 week old spark plugs with new ones and installed a $2 steering cable spacer, tested compression and spark, which was fine, and ran it on the ramp which ran bad but he thought it was just from sucking air sitting still. Hoping it was a fluke, I took it to the lake, launched it and had the same problem I had before I dropped it off, the boat wouldn't even plain out. It sputtered when I pushed the bypass button and throttled it, I could get the rpms up but when it was in gear it was more underpowered and sputtering just the same. My stator is a Mercury brand replacement and only a couple years old. I'm wondering if my sierra switch boxes are defective. I dropped it back off at the marina and the mechanic told me he knows what to look for now and will "run the piss out of it" on the dyno tomorrow and figure out waht's going on. he mentioned timming. I'm learning more but still dumbfounded.
 
An update on my Ignition system. The marina mechanic called me up and let me know that after running some tests, his conclusion was that the ignition system is running properly so the next most likely issue would be carburetors. He told me "I could rebuild them for you but you probably won't want me to for a bill that would be over a grand." I took his advice, brought the boat home and put it in the garage. After looking over an exploded diagram for a while I found online, and buying 3 gasket kits for about 7 bucks a pop, I started tearing the carbs down, cleaning them and reassembling. I also replaced the cheap primer bulb with a nice quicksilver brand. and also replaced a couple other fuel line components with new, better quality stuff, including the fuel line quick disconnect on the motor. After water testing it, the boat starts and idles better than ever, and no more sputtering problem.
 
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