1971 johnson 100hp not firing

[slim82]

I have a 1971 johnson 100 hp model #100ESL71A I was having a problem with having a dead cyl bank on left side of motor facing motor from behind and found i had a worn point that wasn't opening. I replaced points and tried going to lake boat fired right up ran for 10 min at idle and died. I now have no fire to any cylinders. Im thinking my power pack died. I have no power to my coil. I have tried the capacitance discharge test and i cannot get a glow from light at all at blue wire. I have 12.6V at my purple wire for my box. The grey wire on box shows 11.8V with key on but it will not light my test light. Tried disconnecting ground wire for box to check to see if it was a cutoff problem and still did not regain spark. I'm not sure what else to check unless you know of any other test to try. I do not see any bare wires or obvious indication of a short anywhere. Points gapped at .010 and plugs at .030 new wires. my coil is showing approx 255ohms for resistance

 

[R.Johnson]

Re: 1971 johnson 100hp not firing

You must have a OEM manual to trouble shoot this system. Most shop's today won't touch it because they have no one that understand's it. This is what will shut it down, key switch, dirty,worn, or misadjusted points, anti-reverse spring, damaged, or worn rotor, damaged distributor cap, clipper switch, pulse pack, ignition coil. That is a lot of quess's, some very exspensive with out a manual, and at least basic test tool's. Connections to these component's must be sound also.

 

[slim82]

Re: 1971 johnson 100hp not firing

Thanks for some insight. I just printed off a trouble shooting guide i know what everything is except the clipper switch where is this located thanks

 

[R.Johnson]

Re: 1971 johnson 100hp not firing

Just below the junction panel on the back of the engine. Cast aluminum box, 3/4" thick, 2-1/2" long, 1-1/2" wide. 3 wire. Meant to protect the pulse pack from voltage spikes, bad battery connection. Latter taken out of the system when the pulse pack was replaced. Should you need a new pack, replace the coil also. Remove the clipper. If using a Rapair pack, they will void the warranty if the clipper is used.

 

[slim82]

Re: 1971 johnson 100hp not firing

ok thanks for the info i checked my motor out i don't think the clipper is on it anymore so the previous owner must have replaced the pack before and removed the clipper. i am going to order a manual tonight and do some trouble shooting before throwing parts at it. after reading some post on here it kinda sounds uncommon for all four cyl to loose fire when these packs fail so i am going to investigate some more first hopefully i can get her going again.

 

[F_R]

Re: 1971 johnson 100hp not firing

ok thanks for the info i checked my motor out i don't think the clipper is on it anymore so the previous owner must have replaced the pack before and removed the clipper. i am going to order a manual tonight and do some trouble shooting before throwing parts at it. after reading some post on here it kinda sounds uncommon for all four cyl to loose fire when these packs fail so i am going to investigate some more first hopefully i can get her going again.

If the pulse pack fails, you WILL lose all four cylinders. It never fails on just some of them. You mentioned removing the ground wire. Disconnecting wires is a no-no on that system.

 

[slim82]

Re: 1971 johnson 100hp not firing

ok thanks when i said i disconnected the ground wire. i meant the black/yellow or white striped wire for the kill wire my local boat mechanic told me to try and unplug that and see if spark came back thanks ordered a manual it should be here in a couple days

 

[slim82]

Re: 1971 johnson 100hp not firing

finally got my manual everything has checked out in sytems so far haven't been able to test the amplifier box with neon test light because i don't have one. I checked wire output to coil from box using a dva voltmeter and am getting no voltage why cranking motor. I assume amp is bad. when i put a volt meter on the wire for positive side of points i am only reading 5.5 volts going to points if i read the trouble shooting guide correctly there should be battery voltage at the points. I obtained a used box from a salvage type boat shop locally but when i hooked it up i get same no spark result. i checked its voltage to points its putting out 6.5 volts to points. i am not sure if i ended up with a bad box from salvage or if somthing i am missing is causing my problem.

 

[slim82]

Re: 1971 johnson 100hp not firing

forgot to type in i replaced the coil with a new one at time of swaping amplifier boxes any help is greatly apppreciated thanks.

 

[slim82]

Re: 1971 johnson 100hp not firing

got a new amplifier box from CDI replaced box and coil boat ran great last night thanks for all info you have provided