1981 Merc 40hp ignition help

[eclipseturbors]

I picked up a boat that included the motor. The keys were missing, so I picked up a universal 6 position ignition switch. I believe I have it wired correctly with the only question that I connected my purple wire to the "A" connection because there was no "I" connection. The engine cranks kind of when it feels like it though. I hear the solenoid at the starter, but it won't actually crank about half the time. I believe the starter is on it's way out. That's not really my real problem. I have reason to believe that I am getting no fire. I rubber banded my high/low test light to a plug wire and it never lights up when the motor does crank. I also never get any signs of life when some fuel is squirted into the carb. I am trying to follow along the maxrules.com site for troubleshooting the CDI box (the previous owner must have replaced the OEM one with this one) and I seem to be confused. The box has a part# of 114-4911. All of my ohm readings seem to be screwed up. If someone has some expertise on where I'm going wrong, please respond. Also, the rectifier had the terminals where the yellow wires go rusted up a bit. When I tried to remove the nut to clean the terminal, the stud broke. The wires can be rigged back on until I get a new rectifier, but the website says to remove the yellow wires and test for spark, so I left them off. Sorry for the long post, but I am trying to provide enough info to narrow down my problem.

 

[Bill kubiak]

Re: 1981 Merc 40hp ignition help

I have a 97 merc 40 with ignition issues and I have been trying for over a week to get anyone here to respond with advice or help. Apparently all the ignition experts are on vacation at this time.
I wanted to know If I had a weak spark or not. I found a testor at Harbor Freight called an Ignition Trak Testor. it is a simple gadget with a pressure gauge, a clear plastic tube and a second tube with an O ring and some wires with aligator clips. You can wiggle one tube over the other increasing the pressure in the tube. The gauge is marked with red, yellow and green bands. Inside the inner tube are two electrodes. there are two wires, one going to each electrode, one goes to ground, the other to the end of a spark plug lead. You crank the engine over and see if there is a spark jumping the electrodes, if it jumps with the pointer in the green band with a blue spark, your ignition is good, yellow sparlk your ignition is ok but marginal, you can keep reducing the pressure and watch to see where you get a blue spark.
On my engine I got a blue spark at the lowest part of the green band, if I increased the pressure a little I got an intermittent yellow spark, if I incresed it to about the middle of the green bank I got no spark.
It turns out my ignition is pretty good, now my problem is to assure the sparks are occuring at the proper time.
I hope this gives you some ideas

 

[eclipseturbors]

Re: 1981 Merc 40hp ignition help

I'm hoping to be patient and get some great input soon. I've learned to be patient with these things so that I'm buying only the broken part and only doing it once... I'm sure someone will take some time off while at work and help us out. At least this is what I do while "working".

 

[Texasmark]

Re: 1981 Merc 40hp ignition help

I'll attempt to help, but I have never had one of those engines and am not professionally trained.....my education came from the U of Hard Knocks. Grin.

On my engine (90) hp there are 2 yellow wires and they go to the rectifier then voltage regulator and recharge the battery. Obviously problems there result in starting problems, and if the triggers come off that line you could have spark plug firing issues...but mine don't. The purple wire in Merc harnesses is 12v, but switched on when the ignition switch is somewhere besides OFF.

The starter could be just fine...might need some terminal/grounding strap cleaning up, or a new starting solenoid. Starters last a very long time.....besides being expensive. They need a lot of electrical current that you can't get through corroded terminals. Clean and tighten all connections between and including the + and - battery terminals, the battery to engine ground connection and all red wires from the battery+ thru the starting solenoid to the starter....then clean up the ground strap from the engine block to the starter case.

Fuel squirted into the carb with no results says you are chasing an ignition problem.

My test for spark used to be to take a spark plug, remove it from the engine, connect the high voltage lead with the shell touching the engine block and looking for a spark. If it is a nice hot blue spark, then you are usually good to go. If anything else, usually your high voltage components....the module that is connected to the plug wire, is defective.

Don't expect the modules for both plugs to be bad. Usually if that is a problem, the engine will run on 1 cylinder with half fast performance.

If neither work, then it is your trigger module or the stator developing the triggers for you.....if your battery corroded terminals isn't the main issue.

Come back,

Mark

 

[Bill kubiak]

Re: 1981 Merc 40hp ignition help

texasmark, is there a simple test to do to check the trigger and stator with out having all the specialized equipment the dealers have.

I went to a merc dealer today and they are so busy they cannot look at my motor for almost two weeks, they did tell me to try to start the motor with fresh gas as a first step, i did and it did not work.

Even tho I have spark and compression and gas and nothing I think I have weak enough spark to not run the motor