85 hp johnson 1972-help

I have owned my 72 85hp Hydro Electric Shift Johnson (black end plug control box) since about 1978. It has been my baby and always ran great. To me it was the perfect outboard, plenty of power, quiet and smooth running, and great on gas. Now, I have a problem with it and I as well as a few outboard mechanics are stumped. It starts and runs but quits. I could be running full throttle-38-40 mph and BAM it just quits! It almost throws us out of the seats it shuts down so fast. No sputtering, nothing. Completely without warning it just shuts down. Then it won't start at all. I have to wait about 45 minutes and it starts right back up! It is completely unpredictable. Sometimes it will run fine for hours and then other times I can get about 20 minutes out of it. Needless to say we are getting tired of getting towed back to the dock. The motor feels cool to the touch when it breaks down and doesn't appear to be overheating. I had it to the shop several times and have tried and replaced everything 2 or 3 times. Points, coils, dist, wires, plugs, stator, wpump, carbs, fuel filter, etc to no avail. We even replaced the CDI Power Pack 3 times @ 350.00 each! I am actually embarased at how much cash I have sunk into her over this problem. Still the problem exists. I appreciate any insight you guys might have on this. I don't want to get rid of her if I don't have to. Thanks in advance.

Re: 85 hp johnson 1972-help

The battery should be a top notch battery of at least a 70 amp hour rating and fully charged. Make sure that all battery cables are clean and wrench or plier tight (no wing nuts tightened with fingers).

The stator on that model is a set of alternator coils only, meaning it has to do with charging the battery.... and nothing to do with the ignition system.

To have the engine shut down instantly such as turning the key OFF, it would be obvious that the problem is an ignition one. Running out of fuel for any reason would result in a gradual shut down of the engine.

The ignition system is a Battery Capacitance Discharge system, meaning that the pulsepack is dependent on battery voltage in order for it to function. For this system to be intermitent (taking into account that you've replaced the pulsepack several times and it's unlikely that several pulsepacks all have the same flaw), either the 12 volt supply is being interrupted OR a key component has a faulty ground.

Make sure that the pulsepack ground setup is perfect as I've seen a few of those that left something to be desired.

Voltage Source To Pulsepack: Changing that unit so many times, I'm sure you know which wire at the terminal strip powers the pack. Make a RED jumper wire with the proper terminal on the ends so that they will attach properly at that terminal with the other end being able to attach to the positive battery cable terminal of the starter solenoid.

This will throw 12 volts directly to the pulsepack from the battery (same as key ON with no way to turn it OFF), eliminating any other component that might have anything to do with the ignition system. Since it is not fused, keep a pair of wire cutters handy just in case it has to be disconnected quickly. I'd suggest that you attach the terminal strip end first, then the larger one to the solenoid end to eliminate any chance of having sparks fly about (smaller end touching a ground).

If this eliminates the problem, then you'll know that the problem is due to having the pulsepacks 12 volt battery source being interrupted. If the problem still exists, be sure to immediately check that RED jumper wire terminal with a volt meter to see that the proper battery voltage is still there (between small RED wire terminal and pack ground itself). If not..... move the volt meter ground wire to other ground sources to determine a ground break.

Let us know what you find.