1972 Johnson 100HP knocks off after warm up

[jrttoday]

I've had a couple or three mechanics look it over with NO success; if at first you don't succeed.... keep on suckin til ya do succeed!! I have a fair amount of mechanical experience, just not with outboards. It's hard to find anyone having experience with these dinosaurs, so I'm asking here.
Over the past two years, this is what has been done ---- new power pack/coil and rectifier, used stator (checks OK), impeller, carbs rebuilt and fuel lines changed out, new fuel pump, and believe it or not - a brand new still in the box distributor cap! I have a new 1,000 amp battery, good compression (low hours), freshwater only until I bought it five years ago - brackish/fresh now.

THE PROBLEM!!! In the water, after idling out from the ramp, it begins to cut out (depending on how warm the water is/warmer = sooner) and cuts off. It will restart immediately, but after a few times, 1,800rpm is max. At home w/muffs, it knocks off after the engine warms. It's probably simple, just haven't found the answer.
There is/are heat (a) sensor(s) in the head - I only see one lol, Is that the problem? How do you test it? etc etc any help! THANKS!!!

you can teach an old dog new tricks, ya just can't teach a new dog old tricks!! at least it seems that way...... hahahhaaaa

 

[Bosunsmate]

When it cuts out, run a spark tester on it.
Those heat sensors normally only hook up to a horn which sounds if you have an overheat, they wont shut down the motor. They work by grounding out when too hot which completes the horn circuit. You can test them by pulling back the sleeve by the sensor and grounding the wire to a bolt, with the key on the alarm should sound.

 

[jrttoday]

wouldn't that only work while the motor is running? Also, kinda thought a heat sensor was only for warning - just wasn't sure but will test it tomorrow, thanks! Something is wrong somewhere????

 

[Bosunsmate]

just with the key on should be fine.
yes somethings wrong, you arent happy. try a spark test when it cuts out , if theres no spark, then you can narrow it down to electrics

 

[emdsapmgr]

I had a 72 100 hp Johnson. When first purchased it would run for about 10 minutes, then shut off and would not restart. Replaced the timing sensor 385008 in the distributor base plate and it ran like a champ till I traded it.

 

[jrttoday]

that's at least the second time I read something about the timing sensor being problematic while running. Is there a way to test it with the engine off? A timing light would tell me if it is advancing; motor revs fine until it dies - just like you turned the ignition off.
​I really appreciate the responses

 

[jrttoday]

found this online___
1. Disconnect the sensor and check the resistance between the black/white and white/black wires. The reading should be approximately 5-6 ohms. 2. Check for a shortage between the sensor wires and engine ground. If you read a shortage, check the anti-reverse spring and the insulator on the tower to see if they are bent or broken. 3. If the readings above are correct, reset the air gap on the sensor to 0.020 - 0.022 and retest.

 

[Bosunsmate]

You can look it up in here
http://issuu.com/cdielectronics/docs/troubleshootingguide

 

[jrttoday]

really good info!! thanks

 

[jrttoday]

timing sensor checked OK (5.5ohms) and no grounding out. Guess I'll go back to the beginning of issue tomorrow.... After I installed a new power pack two years ago, could get no consistent fire. Took it to a shade tree mechanic and he rewired the remote (said it had issues). Then ran well until warm up. He looked at it again finding nothing wrong (so he said) = problem not fixed. I've had two other so called reputable shops investigate; other than depleting my wallet......
I will disassemble the remote and look it over myself, but I have doubts as to that being the problem.
Short of buying a new outboard, am open to even the most ridiculous suggestions/advice y'all can come up with. Ain't no point in crying!:laugh:

 

[emdsapmgr]

There are some great ignition troubleshooting tips at this website: cdielectronics.com Look for their troubleshooting guide, then for your specific engine. You may find this helpful-certainly better than the original factory manual...

 

[jrttoday]

thanks, been there before and found nothing specific but in looking again found similar enough to re-investigate... Going to consult a boat psychiatrist if problem not resolved soon!!! :lol: BC Powders not effective!!

 

[racerone]

Remove flywheel.----Inspect the anti- reversing spring.--Clean up any metal powder found under there.--Clean distributor cap.--Clean the rotor.-Replace the wee rubber boots on the distributor cap.-----Plug wires thread into the cap.------Inspect wires from anti-reversing spring and the wires from the sensor coil.

 

[jrttoday]

Amazingly, I found a brand new still in the box distributor on ebay 3 weeks ago, didn't necessarily need it, but what a find!! Rotor OK, inspected wires(seemed OK), plug wires good (ends too), boots not torn. It all checks good unless I'm missing something? Washed plate with wire dry spray, no dust. Nothing grounding out, just had it off again today, put back, starts and runs great for about ten minutes good and warm then dies just like you turned the ignition switch off. Will restart immediately, but shuts off sooner and sooner.
To me that seems like heat sensitivity somewhere. [7 pounds water pressure at 800 rpm w/stat open]

 

[jrttoday]

Monkey Nuts!!! will check'em tomorrow. There's one on the back of the motor for the electric shift, and one in the remote tied into the ignition switch. The one in the remote is what needs checking. An old mechanic at the salvage yard said.

 

[jrttoday]

Found an old shop manual on ebay, going through everything again. Reset timing sensor air gap (was to close), have my fingers crossed for tomorrow...

 

[jrttoday]

Well.... it's official, just passed my certification test for insanity!!:lol: just acquired a 115 Johnson - 115esl70d - that's a '70 model hydroelectric shift! lol WTF was I thinking?!! Somebody junked it for some reason?? BUT, almost all the electrical and ignition parts are identical to my 100h. And the powerhead etc etc etc ='s interchangeable!!! :joyous::joyous::joyous: <<that's either Manny, Moe, and Jack or The Three Stooges!

Starter and flywheel look great as do the carburetors. Nothing appears to have ever been separated from the other since birth. Engine block is clean and factory paint is not faded. Lower unit is clean and solid, but the only way I can use it on the 100h is as a whole (from the shaft down/"72 electric shift different than '70)

Seems to have compression, but will not spin it until getting some lubricant in her. Might just rebuild it this winter for something to do? Would be an awesome spare motor; my remote will plug right in.

Yet, I'm still working on the 100h.
Anyway, was adjusting/synchronizing the carburetor linkages with timing linkages yesterday and discovered possibly/probably "why" she won't turn over 4600. I spun the yoke on the throttle cam out 5 full turns!!! Now, the linkages bottom out on the stops (timing advance stop and throttle stop), the butterflies lay flat, and then my timing light died just before a friend called me to tell me about this 115
Don't know if my 100 was set up at the factory that way or if the previous owner had it dialed back? It's always run great, had no complaints - other than 4600 was it no matter the load. Always had plenty of power up till that threshold. NO SHOP has ever adjusted those linkages while I've owned it; perhaps the timing is what has been causing the problem, but I seriously doubt that.

Hope to make time for it today, but..... who knows what's next?

 

[jrttoday]

this is my '72 Johnson 100 - notice the extreme wear on the original starter bendix!!! lol Brand new distributor cap and fuel pump; found insulation broken off at stator and repaired with liquid electric tape. Stator has not yet been re-installed, was thinking I'd use the one off of the 115 I just bought. NOT gonna happen! It will work, but that 115 is in too good a shape to be a parts motor...
http://

 

[jrttoday]

After pulling the flywheel and seeing this, I changed my mind. I figured it would look pretty good, but........ my eyes popped out!!!I doubt a wrench has ever been turned on this motor until today; and I'm only looking
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[jrttoday]

lifting bracket has a crack I'll weld, and one bolt was broken leaving 1/4" protruding; spun out easily w/fingers. Probably due the no towmotor operating son of a biscuit eater that loaded it into my truck. Two plug wires had been cut with a knife; which makes no sense to me??? And the insulator on one plug was cracked, huh??
Had to leave pressure on my flywheel puller for maybe thirty minutes before it popped. No corrosion, just hadn't been off in 45yrs. Wires are really good, sleeve on battery cables dried out on ends (see cracks by starter bendix). And notice the absence of wear on the bendix!! was so excited could hardly get to sleep last night!

That is the original stator and D-cap, starter etc..... This motor must have been kept in a bubble. No soot build up anywhere!! I'm wondering if it was ever broke in? I've developed a great respect for these old V-4 workhorses. It's really too bad and too sad that Made in USA no longer means what it did....
Regardless, there's still a some work to do before turning the key