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Johnson commercial outboard timing specs

C

Capnstern

Member
Hi. I have a 1985 Johnson 100 hp commercial outboard. The model number is J100WMLCOC. I cannot find the wot timing spec anywhere. I have looked many times on the net and here with no luck. What I am seeing is cranking at wot with the timer base rubber stop hitting it's stop is 21 degrees. Of course at wot this should equate to 25 degrees. Is this correct? I've seen older versions this motor spec ed at 28 degrees wide open throttle. It has a stumble off idle which may or may not be related, but I want to make sure I don't damage the engine running at the wrong timing setting. This is how it was set when I got it. Thanks in advance for any help.
 
The timing on these motors simply does not go out of adjustment.-----Post your compression test numbers here.----And does spark jump a gap of 7/16" on each lead using a test device ?----Test run with cowling off the motor.----And test run with another tank and hose.
 
I agree, the timing does not go out of adjustment, but I don't know the history of this engine and have no way of knowing if anybody monkeyed with the timing as if have no idea what it's supposed to be. My compression numbers are 110,100,105,105. Ive had a problem with ignition modules dying on one the port side. I took it out yesterday , throttled up , it stumbled, then took off. Was at 40 mph and could have given it more but didnt. Ran about a mile, then back. Shut it down and had a hard time getting it to start. It did start, but had to limp back to the ramp. At home I discovered ignition box number 3 was doa. I have cleaned and rebuilt carbs, new water pump, ran resistance and DVA tests on every ignition component. All within spec. After module 3 died, I have spent the day swapping stator, timer base and last spare module from my parts motor. It sounded better and is running on all four cylinders. I have also cleaned tank and filled with fresh fuel. Module 1 died before I discovered I had 8 volts on the kill switch wire. Ive since replaced the switch. I did notice I would see about .0012 volts on the kill circuit. For good measure, I bypassed the kill wiring and ran it to the control box side of the red connector. I will work my way thru getting rid of the stumble. I might have to disassemble the carbs again, but working thru everything, I still do not know what wide open spark advance should be. I haven't messed with,it, but I don't know if someone has previously played with it. Sorry for the really long winded reply, but wanted you to know where I stood.
 
Ok. My compression numbers are 110,100,105,105. Spark will easily jump a 7/16" gap and I have totally cleaned the fuel tank. There was no water in it. All the other stuff i did was when I first got it as I knew it needed some work. I just want to verify the timing number is correct. after the last box died, I found where someone routed the timing ring wires incorrectly. One of them had been contacting the flywheel and had rubbed thru the insulation. Could this possibly be the cause as to why the motor stumbled as it did seem sort of random?
 
That's what I am hoping. I haven't had it back in the water yet, but it wouldn't bog every time. The way the wiring was routed it could have very well been randomly touching the flywheel when the timing ring turned. As far as the power packs blowing, one one hand they were all pretty old. I ended up wiring a separate kill switch circuit as I was still getting a few millivolts on the kill switch wire and I have read that even voltage that low will kill a power pack eventually. Since the last timing ring was so "expertly" installed, I still am wondering what the factory WOT timing number is. I cannot find out what It should be. There is a very good chance that this being the commercial version that it would be different from the consumer V4 engines of the era (28 deg I have read)
 
I think i'm going to order it. I've looked on and off for a few months and couldn't find anything that specifically mentioned my motor. Thanks for the help!
 
Actually, I just ordered a hard copy off ebay for $10.14! I have tried and tried to find a manual part number for this engine. The link you sent me had a part number for the manual, so I googled it and easily found it. Thanks again!
 
Some will argue.----In a factory service manual there is no mention of different timing for the V-4 ---" commercial " models.-------And about the only thing different on the commercial model is that they often left the factory with a V-6 lower unit ( heavy duty ) you might say.-----And of course the paint and decals are different !
 
You sir are correct. It came with a v6 lower unit case. Since it is made to push heavy loads I thought it might have a different timing setting. From what I have read , it looks like most v4s seem to be set at 28 degrees? If that is the case, should I reset it to 24 cranking wot? I came from messing with Mercs and I know you could melt a piston if the timing is wrong. What is your opinion?
 
I am going to be blunt again.----You are overthinking.-----There is nothing different about commercial motors.---Often just the lower unit / no oil injection / no electric start either on some ( even V-4 models )
 
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